diff --git a/.github/workflows/deploy-to-dev-ec2.yml b/.github/workflows/deploy-to-dev-ec2.yml
index 5fae574..e949c54 100644
--- a/.github/workflows/deploy-to-dev-ec2.yml
+++ b/.github/workflows/deploy-to-dev-ec2.yml
@@ -75,6 +75,10 @@ jobs:
             WEEKLY_PROMPT="$(printf '%s' "$WEEKLY_PROMPT_B64" | base64 -d | tr -d '\r')"
             export WEEKLY_PROMPT
             
+            MONTHLY_PROMPT_B64="${{ secrets.MONTHLY_PROMPT_B64 }}"
+            MONTHLY_PROMPT="$(printf '%s' "$MONTHLY_PROMPT_B64" | base64 -d | tr -d '\r')"
+            export MONTHLY_PROMPT
+            
             DB_URL="${{ secrets.DB_URL }}" \
             DB_USERNAME="${{ secrets.DB_USERNAME }}" \
             DB_PASSWORD="${{ secrets.DB_PASSWORD }}" \
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/AnswerEntryQueryRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/AnswerEntryQueryRepository.java
index fbaa5d5..13e97bf 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/AnswerEntryQueryRepository.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/AnswerEntryQueryRepository.java
@@ -10,7 +10,6 @@
 
 import java.time.LocalDate;
 import java.util.List;
-import java.util.Optional;
 
 public interface AnswerEntryQueryRepository extends Repository<AnswerEntry, Long> {
 
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/DailyReportRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/DailyReportRepository.java
index eca6a27..9d497e4 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/DailyReportRepository.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/dailyreport/core/repository/DailyReportRepository.java
@@ -58,6 +58,15 @@ default long countCompletedInWeek(Long userId, LocalDate weekStartDate, LocalDat
         );
     }
 
+    default long countCompletedInMonth(Long userId, LocalDate monthStartDate, LocalDate monthEndDate) {
+        return countByAnswerEntry_User_IdAndStatusAndDateBetween(
+                userId,
+                DailyReportStatus.COMPLETED,
+                monthStartDate,
+                monthEndDate
+        );
+    }
+
     @Modifying(clearAutomatically = true, flushAutomatically = true)
     @Query("UPDATE DailyReport w SET w.status = :status WHERE w.id = :id")
     int updateStatus(
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/MonthlyReportController.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/MonthlyReportController.java
new file mode 100644
index 0000000..0c2ca90
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/MonthlyReportController.java
@@ -0,0 +1,151 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.api;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response.MonthlyReportResponse;
+import com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response.MonthlyReportStartResponse;
+import com.devkor.ifive.nadab.domain.monthlyreport.application.MonthlyReportQueryService;
+import com.devkor.ifive.nadab.domain.monthlyreport.application.MonthlyReportService;
+import com.devkor.ifive.nadab.domain.weeklyreport.api.dto.response.CompletedCountResponse;
+import com.devkor.ifive.nadab.global.core.response.ApiResponseDto;
+import com.devkor.ifive.nadab.global.core.response.ApiResponseEntity;
+import com.devkor.ifive.nadab.global.security.principal.UserPrincipal;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.security.SecurityRequirement;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.access.prepost.PreAuthorize;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.*;
+
+@Tag(name = "월간 리포트 API", description = "월간 리포트 생성 및 조회 관련 API")
+@RestController
+@RequestMapping("${api_prefix}/monthly-report")
+@RequiredArgsConstructor
+public class MonthlyReportController {
+
+    private final MonthlyReportService monthlyReportService;
+    private final MonthlyReportQueryService monthlyReportQueryService;
+
+    @PostMapping("/start")
+    @PreAuthorize("isAuthenticated()")
+    @Operation(
+            summary = "월간 리포트 생성 시작",
+            description = """
+                    사용자의 (지난 달에 대한) 월간 리포트 생성을 시작합니다. </br>
+                    비동기로 처리되기 때문에, id로 월간 리포트 조회 API를 폴링하여 상태를 확인할 수 있습니다.
+                    """,
+            security = @SecurityRequirement(name = "bearerAuth"),
+            responses = {
+                    @ApiResponse(
+                            responseCode = "200",
+                            description = "월간 리포트 생성 시작 성공",
+                            content = @Content(schema = @Schema(implementation = MonthlyReportStartResponse.class), mediaType = "application/json")
+                    ),
+                    @ApiResponse(
+                            responseCode = "400",
+                            description = """
+                                    - ErrorCode: MONTHLY_REPORT_NOT_ENOUGH_REPORTS - 월간 리포트 작성 자격 미달 **(이 경우 data의 completedCount 필드에 지난 주에 작성된 오늘의 리포트 수가 포함됩니다.)**
+                                    - ErrorCode: WALLET_INSUFFICIENT_BALANCE - 크리스탈 잔액 부족
+                                    """,
+                            content = @Content(schema = @Schema(implementation = CompletedCountResponse.class), mediaType = "application/json")
+                    ),
+                    @ApiResponse(
+                            responseCode = "401",
+                            description = "인증 실패",
+                            content = @Content
+                    ),
+                    @ApiResponse(
+                            responseCode = "404",
+                            description = """
+                                    - ErrorCode: USER_NOT_FOUND - 사용자를 찾을 수 없음
+                                    - ErrorCode: WALLET_NOT_FOUND - 지갑을 찾을 수 없음
+                                    """,
+                            content = @Content
+                    ),
+                    @ApiResponse(
+                            responseCode = "409",
+                            description = """
+                                    - ErrorCode: MONTHLY_REPORT_ALREADY_COMPLETED - 이미 작성된 월간 리포트가 존재함
+                                    - ErrorCode: MONTHLY_REPORT_IN_PROGRESS - 현재 월간 리포트를 생성 중임
+                                    """,
+                            content = @Content
+                    )
+            }
+    )
+    public ResponseEntity<ApiResponseDto<MonthlyReportStartResponse>> startMonthlyReport(
+            @AuthenticationPrincipal UserPrincipal principal
+    ) {
+        MonthlyReportStartResponse response = monthlyReportService.startMonthlyReport(principal.getId());
+        return ApiResponseEntity.ok(response);
+    }
+
+    @GetMapping
+    @PreAuthorize("isAuthenticated()")
+    @Operation(
+            summary = "나의 월간 리포트 조회",
+            description = "사용자의 (지난 달) 월간 리포트를 조회합니다.",
+            security = @SecurityRequirement(name = "bearerAuth"),
+            responses = {
+                    @ApiResponse(
+                            responseCode = "200",
+                            description = "나의 월간 리포트 조회 성공",
+                            content = @Content(schema = @Schema(implementation = MonthlyReportResponse.class), mediaType = "application/json")
+                    ),
+                    @ApiResponse(
+                            responseCode = "401",
+                            description = "인증 실패",
+                            content = @Content
+                    ),
+                    @ApiResponse(
+                            responseCode = "404",
+                            description = """
+                                    - ErrorCode: USER_NOT_FOUND - 사용자를 찾을 수 없음
+                                    - ErrorCode: MONTHLY_REPORT_NOT_FOUND - 월간 리포트를 찾을 수 없음
+                                    - ErrorCode: MONTHLY_REPORT_NOT_COMPLETED - 해당 월간 리포트가 아직 생성 완료되지 않음
+                                    """,
+                            content = @Content
+                    )
+            }
+    )
+    public ResponseEntity<ApiResponseDto<MonthlyReportResponse>> getLastMonthMonthlyReport(
+            @AuthenticationPrincipal UserPrincipal principal
+    ) {
+        MonthlyReportResponse response = monthlyReportQueryService.getLastMonthMonthlyReport(principal.getId());
+        return ApiResponseEntity.ok(response);
+    }
+
+    @GetMapping("/{id}")
+    @PreAuthorize("isAuthenticated()")
+    @Operation(
+            summary = "id로 월간 리포트 조회",
+            description = """
+                    월간 리포트를 id로 조회합니다. </br>
+                    생성 대기 중인 경우 ```status = "PENDING"``` 으로 반환됩니다. </br>
+                    생성 진행 중인 경우 ```status = "IN_PROGRESS"``` 로 반환됩니다. </br>
+                    생성에 성공한 경우 ```status = "COMPLETED"``` 로 반환됩니다. </br>
+                    생성에 실패한 경우 ```status = "FAILED"``` 로 반환됩니다. 이때 크리스탈이 환불되기 때문에 잔액 조회를 해야합니다.
+                    """,
+            security = @SecurityRequirement(name = "bearerAuth"),
+            responses = {
+                    @ApiResponse(
+                            responseCode = "200",
+                            description = "월간 리포트 조회 성공",
+                            content = @Content(schema = @Schema(implementation = MonthlyReportResponse.class), mediaType = "application/json")
+                    ),
+                    @ApiResponse(
+                            responseCode = "404",
+                            description = "- ErrorCode: MONTHLY_REPORT_NOT_FOUND - 월간 리포트를 찾을 수 없음",
+                            content = @Content
+                    )
+            }
+    )
+    public ResponseEntity<ApiResponseDto<MonthlyReportResponse>> getMonthlyReportById(
+            @PathVariable Long id
+    ) {
+        MonthlyReportResponse response = monthlyReportQueryService.getMonthlyReportById(id);
+        return ApiResponseEntity.ok(response);
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportResponse.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportResponse.java
new file mode 100644
index 0000000..93d6875
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportResponse.java
@@ -0,0 +1,23 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@Schema(description = "월간 리포트 조회 응답")
+public record MonthlyReportResponse(
+
+        @Schema(description = "리포트가 작성된 달")
+        int month,
+
+        @Schema(description = "이런 면도 발견되었어요")
+        String discovered,
+
+        @Schema(description = "이런 점이 좋았어요")
+        String good,
+
+        @Schema(description = "다음엔 이렇게 보완해볼까요?")
+        String improve,
+
+        @Schema(description = "상태", example = "PENDING")
+        String status
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportStartResponse.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportStartResponse.java
new file mode 100644
index 0000000..6dcff7b
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/api/dto/response/MonthlyReportStartResponse.java
@@ -0,0 +1,15 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@Schema(description = "월간 리포트 생성 시작 응답")
+public record MonthlyReportStartResponse(
+        @Schema(description = "생성 예정 월간 리포트 ID", example = "1")
+        Long reportId,
+
+        @Schema(description = "상태", example = "PENDING")
+        String status,
+
+        @Schema(description = "리포트 작성 후 크리스탈 잔액", example = "100")
+        Long balanceAfter
+) {}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportQueryService.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportQueryService.java
new file mode 100644
index 0000000..8108c7f
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportQueryService.java
@@ -0,0 +1,62 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response.MonthlyReportResponse;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReport;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReportStatus;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.repository.MonthlyReportRepository;
+import com.devkor.ifive.nadab.domain.user.core.entity.User;
+import com.devkor.ifive.nadab.domain.user.core.repository.UserRepository;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.NotFoundException;
+import com.devkor.ifive.nadab.global.shared.util.MonthRangeCalculator;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+@Transactional(readOnly = true)
+public class MonthlyReportQueryService {
+
+    private final MonthlyReportRepository monthlyReportRepository;
+    private final UserRepository userRepository;
+
+    public MonthlyReportResponse getLastMonthMonthlyReport(Long userId) {
+        User user = userRepository.findById(userId)
+                .orElseThrow(() -> new NotFoundException(ErrorCode.USER_NOT_FOUND));
+
+        MonthRangeDto range = MonthRangeCalculator.getLastMonthRange();
+
+        MonthlyReport report = monthlyReportRepository.findByUserIdAndMonthStartDate(user.getId(), range.monthStartDate())
+                .orElseThrow(() -> new NotFoundException(ErrorCode.MONTHLY_REPORT_NOT_FOUND));
+
+        if (report.getStatus() != MonthlyReportStatus.COMPLETED) {
+            throw new NotFoundException(ErrorCode.MONTHLY_REPORT_NOT_COMPLETED);
+        }
+
+        return new MonthlyReportResponse(
+                range.monthStartDate().getMonthValue(),
+                report.getDiscovered(),
+                report.getGood(),
+                report.getImprove(),
+                report.getStatus().name()
+        );
+    }
+
+    public MonthlyReportResponse getMonthlyReportById(Long id) {
+        MonthlyReport report = monthlyReportRepository.findById(id)
+                .orElseThrow(() -> new NotFoundException(ErrorCode.MONTHLY_REPORT_NOT_FOUND));
+
+        MonthRangeDto range = MonthRangeCalculator.monthRangeOf(report.getMonthStartDate());
+
+        return new MonthlyReportResponse(
+                range.monthStartDate().getMonthValue(),
+                report.getDiscovered(),
+                report.getGood(),
+                report.getImprove(),
+                report.getStatus().name()
+        );
+    }
+}
+
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportService.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportService.java
new file mode 100644
index 0000000..0f97a8e
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportService.java
@@ -0,0 +1,49 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application;
+
+import com.devkor.ifive.nadab.domain.dailyreport.core.repository.DailyReportRepository;
+import com.devkor.ifive.nadab.domain.monthlyreport.api.dto.response.MonthlyReportStartResponse;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyReserveResultDto;
+import com.devkor.ifive.nadab.domain.user.core.entity.User;
+import com.devkor.ifive.nadab.domain.user.core.repository.UserRepository;
+import com.devkor.ifive.nadab.domain.weeklyreport.api.dto.response.CompletedCountResponse;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.NotFoundException;
+import com.devkor.ifive.nadab.global.exception.report.MonthlyReportNotEligibleException;
+import com.devkor.ifive.nadab.global.shared.util.MonthRangeCalculator;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class MonthlyReportService {
+
+    private final UserRepository userRepository;
+    private final DailyReportRepository dailyReportRepository;
+
+    private final MonthlyReportTxService monthlyReportTxService;
+
+    /**
+     * 비동기 시작 API: 즉시 reportId 반환
+     */
+    public MonthlyReportStartResponse startMonthlyReport(Long userId) {
+        User user = userRepository.findById(userId)
+                .orElseThrow(() -> new NotFoundException(ErrorCode.USER_NOT_FOUND));
+
+        // 월간 리포트 작성 자격 확인 (저번 달에 15회 이상 완료)
+        MonthRangeDto range = MonthRangeCalculator.getLastMonthRange();
+
+        long completedCount = dailyReportRepository.countCompletedInMonth(userId, range.monthStartDate(), range.monthEndDate());
+        boolean eligible = completedCount >= 15;
+
+        if (!eligible) {
+            CompletedCountResponse response = new CompletedCountResponse(completedCount);
+            throw new MonthlyReportNotEligibleException(ErrorCode.MONTHLY_REPORT_NOT_ENOUGH_REPORTS, response);
+        }
+
+        // (Tx) Report(PENDING) + reserve consume + log(PENDING)
+        MonthlyReserveResultDto reserve = monthlyReportTxService.reserveMonthlyAndPublish(user);
+
+        return new MonthlyReportStartResponse(reserve.reportId(), "PENDING", reserve.balanceAfter());
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportTxService.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportTxService.java
new file mode 100644
index 0000000..c5a4601
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/MonthlyReportTxService.java
@@ -0,0 +1,110 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application;
+
+
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyReportGenerationRequestedEventDto;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyReserveResultDto;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReport;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReportStatus;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.repository.MonthlyReportRepository;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.service.PendingMonthlyReportService;
+import com.devkor.ifive.nadab.domain.user.core.entity.User;
+import com.devkor.ifive.nadab.domain.wallet.core.entity.CrystalLog;
+import com.devkor.ifive.nadab.domain.wallet.core.entity.CrystalLogReason;
+import com.devkor.ifive.nadab.domain.wallet.core.entity.UserWallet;
+import com.devkor.ifive.nadab.domain.wallet.core.repository.CrystalLogRepository;
+import com.devkor.ifive.nadab.domain.wallet.core.repository.UserWalletRepository;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.NotEnoughCrystalException;
+import com.devkor.ifive.nadab.global.exception.NotFoundException;
+import lombok.RequiredArgsConstructor;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+@Transactional
+public class MonthlyReportTxService {
+
+    private final PendingMonthlyReportService pendingMonthlyReportService;
+
+    private final MonthlyReportRepository monthlyReportRepository;
+    private final UserWalletRepository userWalletRepository;
+    private final CrystalLogRepository crystalLogRepository;
+
+    private final ApplicationEventPublisher eventPublisher;
+
+    private static final long MONTHLY_REPORT_COST = 40L;
+
+    /**
+     * (Tx) MonthlyReport(PENDING) + reserve consume + CrystalLog(PENDING)
+     * 커밋되면 리포트 생성 작업을 시작할 준비가 완료됨
+     */
+    public MonthlyReserveResultDto reserveMonthly(User user) {
+
+        // Report: 있으면 기존 사용, 없으면 새로 PENDING 생성
+        MonthlyReport report = pendingMonthlyReportService.getOrCreatePendingMonthlyReport(user);
+
+        // 선차감(원자적) + balanceAfter 확보
+        int updated = userWalletRepository.tryConsume(user.getId(), MONTHLY_REPORT_COST);
+        if (updated == 0) {
+            throw new NotEnoughCrystalException(ErrorCode.WALLET_INSUFFICIENT_BALANCE);
+        }
+
+        UserWallet wallet = userWalletRepository.findByUserId(user.getId())
+                .orElseThrow(() -> new NotFoundException(ErrorCode.WALLET_NOT_FOUND));
+        long balanceAfter = wallet.getCrystalBalance();
+
+
+        // 로그(PENDING)
+        CrystalLog log = crystalLogRepository.save(
+                CrystalLog.createPending(
+                        user,
+                        -MONTHLY_REPORT_COST,
+                        balanceAfter,
+                        CrystalLogReason.REPORT_GENERATE_MONTHLY,
+                        "MONTHLY_REPORT",
+                        report.getId()
+                )
+        );
+
+        return new MonthlyReserveResultDto(report.getId(), log.getId(), user.getId(), balanceAfter);
+    }
+
+    public MonthlyReserveResultDto reserveMonthlyAndPublish(User user) {
+        MonthlyReserveResultDto reserve = this.reserveMonthly(user);
+
+        monthlyReportRepository.updateStatus(reserve.reportId(), MonthlyReportStatus.IN_PROGRESS);
+
+        // 트랜잭션 안에서 publish (AFTER_COMMIT 트리거 보장)
+        eventPublisher.publishEvent(new MonthlyReportGenerationRequestedEventDto(
+                reserve.reportId(),
+                user.getId(),
+                reserve.crystalLogId()
+        ));
+
+        return reserve;
+    }
+
+    public void confirmMonthly(Long reportId, Long logId, String discovered, String good, String improve) {
+        // report를 COMPLETED로
+        monthlyReportRepository.markCompleted(reportId, MonthlyReportStatus.COMPLETED, discovered, good, improve);
+
+        // log를 CONFIRMED로
+        crystalLogRepository.markConfirmed(logId);
+    }
+
+    public void failAndRefundMonthly(Long userId, Long reportId, Long logId) {
+        monthlyReportRepository.markFailed(reportId, MonthlyReportStatus.FAILED);
+
+        // 환불(+cost)
+        int updated = userWalletRepository.refund(userId, MONTHLY_REPORT_COST);
+        if (updated == 0) {
+            // wallet이 없을 수 있는 상황
+            throw new NotFoundException(ErrorCode.WALLET_NOT_FOUND);
+        }
+
+        // log를 REFUNDED로
+        crystalLogRepository.markRefunded(logId);
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyRepresentativePicker.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyRepresentativePicker.java
new file mode 100644
index 0000000..940cada
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyRepresentativePicker.java
@@ -0,0 +1,174 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application.helper;
+
+import com.devkor.ifive.nadab.domain.dailyreport.core.entity.EmotionName;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.temporal.WeekFields;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * 월간 리포트 프롬프트에 넣을 "대표 일일 리포트 샘플"을 선정합니다.
+ *
+ * 목표:
+ * 1) 감정 분포 상위 감정 반영(월간 톤/패턴)
+ * 2) 주차 커버리지 확보(특정 며칠에 쏠림 방지)
+ * 3) 정보량(답변/일일리포트 길이) 큰 날 우선
+ *
+ * 출력: 날짜 오름차순 정렬된 대표 샘플 리스트
+ */
+public final class MonthlyRepresentativePicker {
+
+    private MonthlyRepresentativePicker() {
+    }
+
+    public static List<DailyEntryDto> pick(List<DailyEntryDto> entries, int maxSamples) {
+        if (entries == null || entries.isEmpty() || maxSamples <= 0) {
+            return List.of();
+        }
+
+        // 날짜순 정렬(전환점 계산 및 결과 정렬에도 사용)
+        List<DailyEntryDto> sorted = entries.stream()
+                .filter(Objects::nonNull)
+                .sorted(Comparator.comparing(DailyEntryDto::date, Comparator.nullsLast(Comparator.naturalOrder())))
+                .toList();
+
+        // 감정 빈도 집계 (null emotion은 OTHER로 취급)
+        Map<EmotionName, Long> emotionCount = sorted.stream()
+                .map(e -> defaultEmotion(e.emotion()))
+                .collect(Collectors.groupingBy(e -> e, Collectors.counting()));
+
+        Map<LocalDate, Double> scoreByDate = computeScores(sorted, emotionCount);
+
+        // (1) 감정 분포 상위 2개에서 각각 대표 1개씩
+        List<EmotionName> topEmotions = emotionCount.entrySet().stream()
+                .sorted(Map.Entry.<EmotionName, Long>comparingByValue().reversed())
+                .limit(2)
+                .map(Map.Entry::getKey)
+                .toList();
+
+        LinkedHashMap<LocalDate, DailyEntryDto> selected = new LinkedHashMap<>();
+
+        for (EmotionName emo : topEmotions) {
+            pickBestByEmotion(sorted, emo, scoreByDate)
+                    .ifPresent(e -> selected.putIfAbsent(e.date(), e));
+            if (selected.size() >= maxSamples) {
+                return selected.values().stream()
+                        .sorted(Comparator.comparing(DailyEntryDto::date))
+                        .toList();
+            }
+        }
+
+        // (2) 주차(week-of-month)별로 최고점 1개씩 추가해 커버리지 확보
+        WeekFields wf = WeekFields.of(DayOfWeek.MONDAY, 4); // 월요일 시작(한국 기준)
+
+        Map<Integer, List<DailyEntryDto>> byWeek = sorted.stream()
+                .filter(e -> e.date() != null)
+                .collect(Collectors.groupingBy(e -> e.date().get(wf.weekOfMonth())));
+
+        List<Integer> weeks = byWeek.keySet().stream().sorted().toList();
+        for (Integer w : weeks) {
+            if (selected.size() >= maxSamples) break;
+
+            Optional<DailyEntryDto> bestOfWeek = byWeek.get(w).stream()
+                    .filter(e -> !selected.containsKey(e.date()))
+                    .max(Comparator.comparingDouble(e -> scoreByDate.getOrDefault(e.date(), 0.0)));
+
+            bestOfWeek.ifPresent(e -> selected.putIfAbsent(e.date(), e));
+        }
+
+        // (3) 남으면 전체 점수 높은 순으로 채우기
+        if (selected.size() < maxSamples) {
+            List<DailyEntryDto> rest = sorted.stream()
+                    .filter(e -> e.date() != null)
+                    .filter(e -> !selected.containsKey(e.date()))
+                    .sorted((a, b) -> Double.compare(
+                            scoreByDate.getOrDefault(b.date(), 0.0),
+                            scoreByDate.getOrDefault(a.date(), 0.0)
+                    ))
+                    .toList();
+
+            for (DailyEntryDto e : rest) {
+                selected.putIfAbsent(e.date(), e);
+                if (selected.size() >= maxSamples) break;
+            }
+        }
+
+        // 결과는 날짜 오름차순으로(LLM 입력 안정성)
+        return selected.values().stream()
+                .sorted(Comparator.comparing(DailyEntryDto::date))
+                .toList();
+    }
+
+    private static EmotionName defaultEmotion(EmotionName emotion) {
+        return (emotion != null) ? emotion : EmotionName.기타;
+    }
+
+    /**
+     * 점수 구성:
+     * - 정보량: answer/dailyReport 길이 기반
+     * - 희귀 감정 보정: 빈도 낮을수록 가산(inverse)
+     * - 전환점: 전날과 감정이 다르면 가산
+     */
+    private static Map<LocalDate, Double> computeScores(
+            List<DailyEntryDto> sorted,
+            Map<EmotionName, Long> emotionCount
+    ) {
+        long total = emotionCount.values().stream().mapToLong(v -> v).sum();
+        if (total <= 0) total = 1;
+
+        // 희귀도: 빈도 낮을수록 가산
+        Map<EmotionName, Double> rarity = new EnumMap<>(EmotionName.class);
+        for (var e : emotionCount.entrySet()) {
+            double freq = (double) e.getValue() / (double) total; // 0~1
+            rarity.put(e.getKey(), 1.0 + (1.0 - freq) * 1.5);     // 1.0~2.5 정도
+        }
+
+        Map<LocalDate, Double> score = new HashMap<>();
+        DailyEntryDto prev = null;
+
+        for (DailyEntryDto cur : sorted) {
+            if (cur.date() == null) continue;
+
+            int answerLen = safeLen(cur.answer());
+            int reportLen = safeLen(cur.dailyReport());
+
+            // 정보량(로그로 완만하게)
+            double info = Math.log1p(answerLen) * 2.0 + Math.log1p(reportLen) * 1.2;
+
+            EmotionName emo = defaultEmotion(cur.emotion());
+            double rare = rarity.getOrDefault(emo, 1.0);
+
+            // 전환점(전날과 감정이 다르면 +)
+            double change = 0.0;
+            if (prev != null && prev.date() != null) {
+                EmotionName prevEmo = defaultEmotion(prev.emotion());
+                if (!Objects.equals(prevEmo, emo)) {
+                    change = 0.8;
+                }
+            }
+
+            score.put(cur.date(), info * rare + change);
+            prev = cur;
+        }
+
+        return score;
+    }
+
+    private static int safeLen(String s) {
+        return (s == null) ? 0 : s.trim().length();
+    }
+
+    private static Optional<DailyEntryDto> pickBestByEmotion(
+            List<DailyEntryDto> sorted,
+            EmotionName emotion,
+            Map<LocalDate, Double> scoreByDate
+    ) {
+        return sorted.stream()
+                .filter(e -> e.date() != null)
+                .filter(e -> Objects.equals(defaultEmotion(e.emotion()), emotion))
+                .max(Comparator.comparingDouble(e -> scoreByDate.getOrDefault(e.date(), 0.0)));
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyWeeklySummariesAssembler.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyWeeklySummariesAssembler.java
new file mode 100644
index 0000000..bb49d2f
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/helper/MonthlyWeeklySummariesAssembler.java
@@ -0,0 +1,56 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application.helper;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyWeeklySummaryInputDto;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+
+public final class MonthlyWeeklySummariesAssembler {
+
+    private static final String NA = "N/A";
+
+    private MonthlyWeeklySummariesAssembler() {
+    }
+
+    /**
+     * 프롬프트에 넣을 weeklySummaries 텍스트를 생성합니다.
+     *
+     * 예)
+     * - W1(2026-01-01 ~ 2026-01-07)
+     *   discovered: ...
+     *   good: ...
+     *   improve: ...
+     */
+    public static String assemble(List<MonthlyWeeklySummaryInputDto> inputs) {
+        if (inputs == null || inputs.isEmpty()) return "";
+
+        List<MonthlyWeeklySummaryInputDto> sorted = inputs.stream()
+                .filter(Objects::nonNull)
+                .sorted(Comparator.comparing(MonthlyWeeklySummaryInputDto::weekStartDate,
+                        Comparator.nullsLast(Comparator.naturalOrder())))
+                .toList();
+
+        StringBuilder sb = new StringBuilder();
+        int idx = 1;
+
+        for (MonthlyWeeklySummaryInputDto w : sorted) {
+            sb.append("- W").append(idx)
+                    .append("(").append(valueOrNa(w.weekStartDate() == null ? null : w.weekStartDate().toString()))
+                    .append(" ~ ").append(valueOrNa(w.weekEndDate() == null ? null : w.weekEndDate().toString()))
+                    .append(")\n")
+                    .append("  discovered: ").append(valueOrNa(w.discovered())).append("\n")
+                    .append("  good: ").append(valueOrNa(w.good())).append("\n")
+                    .append("  improve: ").append(valueOrNa(w.improve())).append("\n\n");
+            idx++;
+        }
+
+        return sb.toString().trim();
+    }
+
+    private static String valueOrNa(String s) {
+        if (s == null) return NA;
+        String t = s.trim();
+        return t.isEmpty() ? NA : t;
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/listener/MonthlyReportGenerationListener.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/listener/MonthlyReportGenerationListener.java
new file mode 100644
index 0000000..ba7c121
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/application/listener/MonthlyReportGenerationListener.java
@@ -0,0 +1,99 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.application.listener;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.application.MonthlyReportTxService;
+import com.devkor.ifive.nadab.domain.monthlyreport.application.helper.MonthlyRepresentativePicker;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.AiMonthlyReportResultDto;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyReportGenerationRequestedEventDto;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.repository.MonthlyQueryRepository;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.service.MonthlyWeeklySummariesService;
+import com.devkor.ifive.nadab.domain.monthlyreport.infra.MonthlyReportLlmClient;
+import com.devkor.ifive.nadab.domain.weeklyreport.application.helper.WeeklyEntriesAssembler;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
+import com.devkor.ifive.nadab.global.shared.util.MonthRangeCalculator;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+import java.util.List;
+
+@Component
+@RequiredArgsConstructor
+@Slf4j
+public class MonthlyReportGenerationListener {
+
+    private final MonthlyQueryRepository monthlyQueryRepository;
+
+    private final MonthlyReportLlmClient monthlyReportLlmClient;
+    private final MonthlyReportTxService monthlyReportTxService;
+    private final MonthlyWeeklySummariesService monthlyWeeklySummariesService;
+
+    private static final int MAX_LEN = 240;
+
+    @Async("monthlyReportTaskExecutor")
+    @TransactionalEventListener(phase =
+            TransactionPhase.AFTER_COMMIT)
+    public void handle(MonthlyReportGenerationRequestedEventDto event) {
+
+        MonthRangeDto range = MonthRangeCalculator.getLastMonthRange();
+
+        // 1. 일간 리포트 대표 항목 선택
+        List<DailyEntryDto> rows = monthlyQueryRepository.findMonthlyInputs(event.userId(), range.monthStartDate(), range.monthEndDate());
+        List<DailyEntryDto> entries = MonthlyRepresentativePicker.pick(rows, 6);
+        String representativeEntries = WeeklyEntriesAssembler.assemble(entries);
+
+        // 2. 주간 리포트 선택
+        String weeklySummaries = monthlyWeeklySummariesService.buildWeeklySummaries(event.userId(), range);
+
+        AiMonthlyReportResultDto dto;
+        try {
+            // 트랜잭션 밖(백그라운드)에서 LLM 호출
+            dto = monthlyReportLlmClient.generate(
+                    range.monthStartDate().toString(), range.monthEndDate().toString(), weeklySummaries, representativeEntries);
+        } catch (Exception e) {
+            log.error("[MONTHLY_REPORT][LLM_FAILED] userId={}, reportId={}",
+                    event.userId(), event.reportId(), e);
+
+            // 실패 확정 + 환불은 별도 트랜잭션에서
+            monthlyReportTxService.failAndRefundMonthly(
+                    event.userId(),
+                    event.reportId(),
+                    event.crystalLogId()
+            );
+            return;
+        }
+
+        // 성공 확정(별도 트랜잭션)
+        try {
+            monthlyReportTxService.confirmMonthly(
+                    event.reportId(),
+                    event.crystalLogId(),
+                    cut(dto.discovered()),
+                    cut(dto.good()),
+                    cut(dto.improve())
+            );
+        } catch (Exception e) {
+            log.error("[MONTHLY_REPORT][CONFIRM_FAILED] userId={}, reportId={}, crystalLogId={}",
+                    event.userId(), event.reportId(), event.crystalLogId(), e);
+
+            // 저장 실패면 결과를 못 주는 거니까 "실패 확정 + 환불"로 처리
+            monthlyReportTxService.failAndRefundMonthly(
+                    event.userId(),
+                    event.reportId(),
+                    event.crystalLogId()
+            );
+        }
+
+    }
+
+    // 최대 길이 자르기
+    private String cut(String s) {
+        if (s == null) return null;
+        s = s.trim();
+        return (s.length() <= MAX_LEN) ? s : s.substring(0, MAX_LEN);
+    }
+}
+
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/AiMonthlyReportResultDto.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/AiMonthlyReportResultDto.java
new file mode 100644
index 0000000..e930976
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/AiMonthlyReportResultDto.java
@@ -0,0 +1,8 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.dto;
+
+public record AiMonthlyReportResultDto(
+        String discovered,
+        String good,
+        String improve
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/LlmMonthlyResultDto.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/LlmMonthlyResultDto.java
new file mode 100644
index 0000000..ddcdacc
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/LlmMonthlyResultDto.java
@@ -0,0 +1,8 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.dto;
+
+public record LlmMonthlyResultDto(
+        String discovered,
+        String good,
+        String improve
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReportGenerationRequestedEventDto.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReportGenerationRequestedEventDto.java
new file mode 100644
index 0000000..e8bf663
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReportGenerationRequestedEventDto.java
@@ -0,0 +1,8 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.dto;
+
+public record MonthlyReportGenerationRequestedEventDto(
+        Long reportId,
+        Long userId,
+        Long crystalLogId
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReserveResultDto.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReserveResultDto.java
new file mode 100644
index 0000000..432913a
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyReserveResultDto.java
@@ -0,0 +1,9 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.dto;
+
+public record MonthlyReserveResultDto(
+        Long reportId,
+        Long crystalLogId,
+        Long userId,
+        Long balanceAfter
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyWeeklySummaryInputDto.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyWeeklySummaryInputDto.java
new file mode 100644
index 0000000..291d383
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/dto/MonthlyWeeklySummaryInputDto.java
@@ -0,0 +1,12 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.dto;
+
+import java.time.LocalDate;
+
+public record MonthlyWeeklySummaryInputDto(
+        LocalDate weekStartDate,
+        LocalDate weekEndDate,
+        String discovered,
+        String good,
+        String improve
+) {
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReport.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReport.java
new file mode 100644
index 0000000..8b19db1
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReport.java
@@ -0,0 +1,75 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.entity;
+
+import com.devkor.ifive.nadab.domain.user.core.entity.User;
+import jakarta.persistence.*;
+import lombok.*;
+
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+
+@Entity
+@Table(
+        name = "monthly_reports",
+        uniqueConstraints = {
+                @UniqueConstraint(
+                        name = "uq_monthly_reports_user_month",
+                        columnNames = {"user_id", "month_start_date"}
+                )
+        }
+)
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class MonthlyReport {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @ManyToOne(fetch = FetchType.LAZY, optional = false)
+    @JoinColumn(name = "user_id", nullable = false)
+    private User user;
+
+    @Column(name = "month_start_date", nullable = false)
+    private LocalDate monthStartDate;
+
+    @Column(name = "month_end_date", nullable = false)
+    private LocalDate monthEndDate;
+
+    @Column(name = "discovered", length = 250)
+    private String discovered;
+
+    @Column(name = "good", length = 250)
+    private String good;
+
+    @Column(name = "improve", length = 250)
+    private String improve;
+
+    @Enumerated(EnumType.STRING)
+    @Column(name = "status", nullable = false, length = 16)
+    private MonthlyReportStatus status;
+
+    @Column(name = "date", nullable = false)
+    private LocalDate date;
+
+    @Column(name = "analyzed_at")
+    private OffsetDateTime analyzedAt;
+
+    public static MonthlyReport create(User user, LocalDate monthStartDate, LocalDate monthEndDate,
+                                      String discovered, String good, String improve,
+                                      LocalDate date, MonthlyReportStatus status) {
+        MonthlyReport mr = new MonthlyReport();
+        mr.user = user;
+        mr.monthStartDate = monthStartDate;
+        mr.monthEndDate = monthEndDate;
+        mr.discovered = discovered;
+        mr.good = good;
+        mr.improve = improve;
+        mr.date = date;
+        mr.status = status;
+        return mr;
+    }
+
+    public static MonthlyReport createPending(User user, LocalDate monthStartDate, LocalDate monthEndDate, LocalDate date) {
+        return create(user, monthStartDate, monthEndDate, null, null, null, date, MonthlyReportStatus.PENDING);
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReportStatus.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReportStatus.java
new file mode 100644
index 0000000..ed88e74
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/entity/MonthlyReportStatus.java
@@ -0,0 +1,8 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.entity;
+
+public enum MonthlyReportStatus {
+    PENDING,
+    COMPLETED,
+    FAILED,
+    IN_PROGRESS
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyQueryRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyQueryRepository.java
new file mode 100644
index 0000000..cc82e6f
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyQueryRepository.java
@@ -0,0 +1,40 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.repository;
+
+import com.devkor.ifive.nadab.domain.dailyreport.core.entity.AnswerEntry;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.time.LocalDate;
+import java.util.List;
+
+public interface MonthlyQueryRepository extends JpaRepository<AnswerEntry, Long> {
+
+    /**
+     * 월간 리포트 작성을 위한 입력 데이터 조회
+     */
+    @Query("""
+    select new com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto(
+        ae.date,
+        dq.questionText,
+        ae.content,
+        dr.content,
+        em.name
+    )
+    from AnswerEntry ae
+    join ae.question dq
+    left join DailyReport dr
+           on dr.answerEntry = ae
+          and dr.status = com.devkor.ifive.nadab.domain.dailyreport.core.entity.DailyReportStatus.COMPLETED
+    left join dr.emotion em
+    where ae.user.id = :userId
+      and ae.date between :monthStart and :monthEnd
+    order by ae.date asc
+""")
+    List<DailyEntryDto> findMonthlyInputs(
+            @Param("userId") Long userId,
+            @Param("monthStart") LocalDate monthStart,
+            @Param("monthEnd") LocalDate monthEnd
+    );
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyReportRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyReportRepository.java
new file mode 100644
index 0000000..b6b5b17
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/repository/MonthlyReportRepository.java
@@ -0,0 +1,61 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.repository;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReport;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReportStatus;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.time.LocalDate;
+import java.util.Optional;
+
+public interface MonthlyReportRepository extends JpaRepository<MonthlyReport, Long> {
+
+    Optional<MonthlyReport> findByUserIdAndMonthStartDate(Long userId, LocalDate monthStartDate);
+
+    /**
+     * PENDING -> COMPLETED 확정
+     * - 분석 결과(discovered/good/improve) 저장
+     * - analyzedAt 기록
+     */
+    @Modifying(clearAutomatically = true, flushAutomatically = true)
+    @Query("""
+    UPDATE MonthlyReport mr
+       SET mr.status = :status,
+           mr.discovered = :discovered,
+           mr.good = :good,
+           mr.improve = :improve,
+           mr.analyzedAt = CURRENT_TIMESTAMP
+     WHERE mr.id = :reportId
+""")
+    int markCompleted(
+            @Param("reportId") Long reportId,
+            @Param("status") MonthlyReportStatus status,
+            @Param("discovered") String discovered,
+            @Param("good") String good,
+            @Param("improve") String improve
+    );
+
+    /**
+     * PENDING -> FAILED 확정
+     */
+    @Modifying(clearAutomatically = true, flushAutomatically = true)
+    @Query("""
+    UPDATE MonthlyReport mr
+       SET mr.status = :status,
+           mr.analyzedAt = CURRENT_TIMESTAMP
+     WHERE mr.id = :reportId
+""")
+    int markFailed(
+            @Param("reportId") Long reportId,
+            @Param("status") MonthlyReportStatus status
+    );
+
+    @Modifying(clearAutomatically = true, flushAutomatically = true)
+    @Query("UPDATE MonthlyReport m SET m.status = :status WHERE m.id = :id")
+    int updateStatus(
+            @Param("id") Long id,
+            @Param("status") MonthlyReportStatus status
+    );
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/MonthlyWeeklySummariesService.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/MonthlyWeeklySummariesService.java
new file mode 100644
index 0000000..c9f5df0
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/MonthlyWeeklySummariesService.java
@@ -0,0 +1,43 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.service;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.application.helper.MonthlyWeeklySummariesAssembler;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.MonthlyWeeklySummaryInputDto;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.entity.WeeklyReport;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.entity.WeeklyReportStatus;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.repository.WeeklyReportRepository;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Service
+@RequiredArgsConstructor
+@Transactional
+public class MonthlyWeeklySummariesService {
+
+    private final WeeklyReportRepository weeklyReportRepository;
+
+    public String buildWeeklySummaries(Long userId, MonthRangeDto monthRange) {
+        List<WeeklyReport> weeklyReports =
+                weeklyReportRepository.findMonthlyOverlappedWeeklyReports(
+                        userId,
+                        monthRange.monthStartDate(),
+                        monthRange.monthEndDate(),
+                        WeeklyReportStatus.COMPLETED
+                );
+
+        List<MonthlyWeeklySummaryInputDto> inputs = weeklyReports.stream()
+                .map(wr -> new MonthlyWeeklySummaryInputDto(
+                        wr.getWeekStartDate(),
+                        wr.getWeekEndDate(),
+                        wr.getDiscovered(),
+                        wr.getGood(),
+                        wr.getImprove()
+                ))
+                .toList();
+
+        return MonthlyWeeklySummariesAssembler.assemble(inputs);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/PendingMonthlyReportService.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/PendingMonthlyReportService.java
new file mode 100644
index 0000000..7d6707a
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/core/service/PendingMonthlyReportService.java
@@ -0,0 +1,52 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.core.service;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReport;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReportStatus;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.repository.MonthlyReportRepository;
+import com.devkor.ifive.nadab.domain.user.core.entity.User;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.ConflictException;
+import com.devkor.ifive.nadab.global.shared.util.MonthRangeCalculator;
+import com.devkor.ifive.nadab.global.shared.util.TodayDateTimeProvider;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.time.LocalDate;
+
+@Service
+@RequiredArgsConstructor
+public class PendingMonthlyReportService {
+
+    private final MonthlyReportRepository monthlyReportRepository;
+
+    @Transactional
+    public MonthlyReport getOrCreatePendingMonthlyReport(User user) {
+
+        MonthRangeDto range = MonthRangeCalculator.getLastMonthRange();
+        LocalDate today = TodayDateTimeProvider.getTodayDate();
+
+        MonthlyReport report = monthlyReportRepository.findByUserIdAndMonthStartDate(user.getId(), range.monthStartDate())
+                .orElseGet(() -> monthlyReportRepository.save(MonthlyReport.createPending(
+                        user,
+                        range.monthStartDate(),
+                        range.monthEndDate(),
+                        today
+                )));
+
+        if (report.getStatus() == MonthlyReportStatus.COMPLETED) {
+            throw new ConflictException(ErrorCode.MONTHLY_REPORT_ALREADY_COMPLETED);
+        }
+
+        if (report.getStatus() == MonthlyReportStatus.IN_PROGRESS) {
+            throw new ConflictException(ErrorCode.MONTHLY_REPORT_IN_PROGRESS);
+        }
+
+        if (report.getStatus() == MonthlyReportStatus.FAILED) {
+            monthlyReportRepository.updateStatus(report.getId(), MonthlyReportStatus.PENDING);
+        }
+
+        return report;
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/infra/MonthlyReportLlmClient.java b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/infra/MonthlyReportLlmClient.java
new file mode 100644
index 0000000..e9e19d8
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/domain/monthlyreport/infra/MonthlyReportLlmClient.java
@@ -0,0 +1,71 @@
+package com.devkor.ifive.nadab.domain.monthlyreport.infra;
+
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.AiMonthlyReportResultDto;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.dto.LlmMonthlyResultDto;
+import com.devkor.ifive.nadab.global.core.prompt.monthly.MonthlyReportPromptLoader;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.ai.AiResponseParseException;
+import com.devkor.ifive.nadab.global.exception.ai.AiServiceUnavailableException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import lombok.RequiredArgsConstructor;
+import org.springframework.ai.chat.client.ChatClient;
+import org.springframework.ai.openai.OpenAiChatOptions;
+import org.springframework.ai.openai.api.OpenAiApi;
+import org.springframework.stereotype.Component;
+
+@Component
+@RequiredArgsConstructor
+public class MonthlyReportLlmClient {
+
+    private final ChatClient chatClient;
+    private final MonthlyReportPromptLoader monthlyReportPromptLoader;
+    private final ObjectMapper objectMapper;
+
+    public AiMonthlyReportResultDto generate(
+            String monthStartDate, String monthEndDate, String weeklySummaries, String representativeEntries) {
+        String prompt = monthlyReportPromptLoader.loadPrompt()
+                .replace("{monthStartDate}", monthStartDate)
+                .replace("{monthEndDate}", monthEndDate)
+                .replace("{weeklySummaries}", weeklySummaries)
+                .replace("{representativeEntries}", representativeEntries);
+
+        OpenAiChatOptions options = OpenAiChatOptions.builder()
+                .model(OpenAiApi.ChatModel.GPT_5_MINI)
+                .reasoningEffort("low")
+                .temperature(1.0)
+                .build();
+
+        String content = chatClient.prompt()
+                .user(prompt)
+                .options(options)
+                .call()
+                .content();
+
+        if (content == null || content.trim().isEmpty()) {
+            throw new AiServiceUnavailableException(ErrorCode.AI_NO_RESPONSE);
+        }
+
+        try {
+            LlmMonthlyResultDto result = objectMapper.readValue(content, LlmMonthlyResultDto.class);
+
+            String discovered = result.discovered();
+            String good = result.good();
+            String improve = result.improve();
+
+            if (isBlank(discovered) || isBlank(good) || isBlank(improve)) {
+                throw new AiResponseParseException(ErrorCode.AI_RESPONSE_FORMAT_INVALID);
+            }
+
+            return new AiMonthlyReportResultDto(discovered, good, improve);
+
+        } catch (AiResponseParseException e) {
+            throw e;
+        } catch (Exception e) {
+            throw new AiResponseParseException(ErrorCode.AI_RESPONSE_PARSE_FAILED);
+        }
+    }
+
+    private boolean isBlank(String s) {
+        return s == null || s.trim().isEmpty();
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/test/api/TestController.java b/src/main/java/com/devkor/ifive/nadab/domain/test/api/TestController.java
index 19434e4..6a8081b 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/test/api/TestController.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/test/api/TestController.java
@@ -146,4 +146,34 @@ public ResponseEntity<ApiResponseDto<Void>> deleteWeeklyReport(
         testReportService.deleteThisWeekWeeklyReport(principal.getId());
         return ApiResponseEntity.noContent();
     }
+
+    @PostMapping("/delete/monthly-report")
+    @PreAuthorize("isAuthenticated()")
+    @Operation(
+            summary = "(테스트용) 월간 리포트 삭제 API",
+            description = """
+                    이번 달에 생성된 월간 리포트를 삭제합니다. <br/>
+                    생성된 리포트만 삭제 가능합니다. <br/>
+                    크리스탈 또한 환불됩니다.
+                    """,
+            security = @SecurityRequirement(name = "bearerAuth"),
+            responses = {
+                    @ApiResponse(
+                            responseCode = "204",
+                            description = "테스트용 월간 리포트 삭제 성공",
+                            content = @Content
+                    ),
+                    @ApiResponse(
+                            responseCode = "401",
+                            description = "인증 실패",
+                            content = @Content
+                    )
+            }
+    )
+    public ResponseEntity<ApiResponseDto<Void>> deleteMonthlyReport(
+            @AuthenticationPrincipal UserPrincipal principal
+    ) {
+        testReportService.deleteThisMonthMonthlyReport(principal.getId());
+        return ApiResponseEntity.noContent();
+    }
 }
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/test/application/TestReportService.java b/src/main/java/com/devkor/ifive/nadab/domain/test/application/TestReportService.java
index 85536a7..95e7adf 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/test/application/TestReportService.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/test/application/TestReportService.java
@@ -1,5 +1,8 @@
 package com.devkor.ifive.nadab.domain.test.application;
 
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReport;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.entity.MonthlyReportStatus;
+import com.devkor.ifive.nadab.domain.monthlyreport.core.repository.MonthlyReportRepository;
 import com.devkor.ifive.nadab.domain.test.api.dto.request.PromptTestDailyReportRequest;
 import com.devkor.ifive.nadab.domain.test.api.dto.request.TestDailyReportRequest;
 import com.devkor.ifive.nadab.domain.test.api.dto.response.TestDailyReportResponse;
@@ -21,7 +24,9 @@
 import com.devkor.ifive.nadab.global.exception.NotFoundException;
 import com.devkor.ifive.nadab.global.exception.ai.AiResponseParseException;
 import com.devkor.ifive.nadab.global.exception.ai.AiServiceUnavailableException;
+import com.devkor.ifive.nadab.global.shared.util.MonthRangeCalculator;
 import com.devkor.ifive.nadab.global.shared.util.WeekRangeCalculator;
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
 import com.devkor.ifive.nadab.global.shared.util.dto.WeekRangeDto;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import lombok.RequiredArgsConstructor;
@@ -40,10 +45,12 @@ public class TestReportService {
 
     private final UserRepository userRepository;
     private final WeeklyReportRepository weeklyReportRepository;
+    private final MonthlyReportRepository monthlyReportRepository;
     private final TestCrystalLogRepository testCrystalLogRepository;
     private final UserWalletRepository userWalletRepository;
 
-    private static final long WEEKLY_REPORT_COST = 30L;
+    private static final long WEEKLY_REPORT_COST = 20L;
+    private static final long MONTHLY_REPORT_COST = 40L;
 
     @Transactional
     public TestDailyReportResponse generateTestDailyReport(TestDailyReportRequest request) {
@@ -175,4 +182,47 @@ public void deleteThisWeekWeeklyReport(Long userId) {
 
         weeklyReportRepository.delete(report);
     }
+
+    @Transactional
+    public void deleteThisMonthMonthlyReport(Long userId) {
+        User user = userRepository.findById(userId)
+                .orElseThrow(() -> new NotFoundException(ErrorCode.USER_NOT_FOUND));
+
+        MonthRangeDto range = MonthRangeCalculator.getLastMonthRange();
+
+        MonthlyReport report = monthlyReportRepository.findByUserIdAndMonthStartDate(user.getId(), range.monthStartDate())
+                .orElseThrow(() -> new NotFoundException(ErrorCode.MONTHLY_REPORT_NOT_FOUND));
+
+        if (report.getStatus() != MonthlyReportStatus.COMPLETED) {
+            throw new BadRequestException(ErrorCode.MONTHLY_REPORT_NOT_COMPLETED);
+        }
+
+        CrystalLog purchaseLog = testCrystalLogRepository
+                .findByUserIdAndRefTypeAndRefIdAndReasonAndStatus(
+                        userId,
+                        "MONTHLY_REPORT",
+                        report.getId(),
+                        CrystalLogReason.REPORT_GENERATE_MONTHLY,
+                        CrystalLogStatus.CONFIRMED
+                )
+                .orElseThrow(() -> new BadRequestException(ErrorCode.CRYSTAL_LOG_NOT_FOUND));
+
+        int updated = userWalletRepository.refund(user.getId(), MONTHLY_REPORT_COST);
+        if (updated == 0) {
+            throw new NotFoundException(ErrorCode.WALLET_NOT_FOUND);
+        }
+
+        UserWallet wallet = userWalletRepository.findByUserId(userId)
+                .orElseThrow(() -> new NotFoundException(ErrorCode.WALLET_NOT_FOUND));
+        long balanceAfter = wallet.getCrystalBalance();
+
+
+        CrystalLog refundLog = CrystalLog.createConfirmed(user, MONTHLY_REPORT_COST, balanceAfter,
+                CrystalLogReason.TEST_DELETE_REPORT_REFUND_MONTHLY, "MONTHLY_REPORT_REFUND", report.getId());
+        testCrystalLogRepository.save(refundLog);
+
+        testCrystalLogRepository.markRefunded(purchaseLog.getId());
+
+        monthlyReportRepository.delete(report);
+    }
 }
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/wallet/core/entity/CrystalLogReason.java b/src/main/java/com/devkor/ifive/nadab/domain/wallet/core/entity/CrystalLogReason.java
index 074f518..63e76c9 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/wallet/core/entity/CrystalLogReason.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/wallet/core/entity/CrystalLogReason.java
@@ -9,6 +9,7 @@ public enum CrystalLogReason {
     REPORT_GENERATE_ALL,
 
     TEST_DELETE_REPORT_REFUND_WEEKLY,
+    TEST_DELETE_REPORT_REFUND_MONTHLY,
 
     ADMIN_ADJUST
 }
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportService.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportService.java
index 7fb33fe..8bcc2af 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportService.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportService.java
@@ -3,13 +3,10 @@
 import com.devkor.ifive.nadab.domain.dailyreport.core.repository.DailyReportRepository;
 import com.devkor.ifive.nadab.domain.user.core.entity.User;
 import com.devkor.ifive.nadab.domain.user.core.repository.UserRepository;
-import com.devkor.ifive.nadab.domain.wallet.core.entity.UserWallet;
-import com.devkor.ifive.nadab.domain.wallet.core.repository.UserWalletRepository;
 import com.devkor.ifive.nadab.domain.weeklyreport.api.dto.response.CompletedCountResponse;
 import com.devkor.ifive.nadab.domain.weeklyreport.api.dto.response.WeeklyReportStartResponse;
 import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReserveResultDto;
 import com.devkor.ifive.nadab.global.core.response.ErrorCode;
-import com.devkor.ifive.nadab.global.exception.BadRequestException;
 import com.devkor.ifive.nadab.global.exception.NotFoundException;
 import com.devkor.ifive.nadab.global.exception.report.WeeklyReportNotEligibleException;
 import com.devkor.ifive.nadab.global.shared.util.WeekRangeCalculator;
@@ -23,27 +20,21 @@ public class WeeklyReportService {
 
     private final UserRepository userRepository;
     private final DailyReportRepository dailyReportRepository;
-    private final UserWalletRepository userWalletRepository;
 
     private final WeeklyReportTxService weeklyReportTxService;
 
-    private static final long WEEKLY_REPORT_COST = 30L;
-
     /**
      * 비동기 시작 API: 즉시 reportId 반환
      */
     public WeeklyReportStartResponse startWeeklyReport(Long userId) {
         User user = userRepository.findById(userId)
                 .orElseThrow(() -> new NotFoundException(ErrorCode.USER_NOT_FOUND));
-        UserWallet wallet = userWalletRepository.findByUserId(userId)
-                .orElseThrow(() -> new NotFoundException(ErrorCode.WALLET_NOT_FOUND));
-
 
-        // 주간 리포트 작성 자격 확인 (저번 주에 4회 이상 완료)
+        // 주간 리포트 작성 자격 확인 (저번 주에 3회 이상 완료)
         WeekRangeDto range = WeekRangeCalculator.getLastWeekRange();
 
         long completedCount = dailyReportRepository.countCompletedInWeek(userId, range.weekStartDate(), range.weekEndDate());
-        boolean eligible = completedCount >= 4;
+        boolean eligible = completedCount >= 3;
 
         if (!eligible) {
             CompletedCountResponse response = new CompletedCountResponse(completedCount);
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportTxService.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportTxService.java
index 6090801..0b18c4d 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportTxService.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/WeeklyReportTxService.java
@@ -33,7 +33,7 @@ public class WeeklyReportTxService {
 
     private final ApplicationEventPublisher eventPublisher;
 
-    private static final long WEEKLY_REPORT_COST = 30L;
+    private static final long WEEKLY_REPORT_COST = 20L;
 
     /**
      * (Tx) WeeklyReport(PENDING) + reserve consume + CrystalLog(PENDING)
@@ -86,7 +86,7 @@ public WeeklyReserveResultDto reserveWeeklyAndPublish(User user) {
     }
 
     public void confirmWeekly(Long reportId, Long logId, String discovered, String good, String improve) {
-        // 네 weekly_report schema에 맞춰 markCompleted 파라미터 변경
+        // report를 COMPLETED로
         weeklyReportRepository.markCompleted(reportId, WeeklyReportStatus.COMPLETED, discovered, good, improve);
 
         // log를 CONFIRMED로
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyEntriesAssembler.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyEntriesAssembler.java
index daadbf8..a37301b 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyEntriesAssembler.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyEntriesAssembler.java
@@ -1,7 +1,7 @@
 package com.devkor.ifive.nadab.domain.weeklyreport.application.helper;
 
 import com.devkor.ifive.nadab.domain.dailyreport.core.entity.EmotionName;
-import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReportEntryInputDto;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
 
 import java.util.Comparator;
 import java.util.List;
@@ -14,20 +14,26 @@ public final class WeeklyEntriesAssembler {
     private WeeklyEntriesAssembler() {
     }
 
-    public static String assemble(List<WeeklyReportEntryInputDto> inputs) {
+    /**
+     * 프롬프트에 넣을 entries 문자열을 생성합니다.
+     * - date 오름차순 정렬
+     * - D1, D2 ... 번호 부여
+     * - null/blank 값은 N/A로 대체
+     */
+    public static String assemble(List<DailyEntryDto> inputs) {
         if (inputs == null || inputs.isEmpty()) {
             return "";
         }
 
-        List<WeeklyReportEntryInputDto> sorted = inputs.stream()
+        List<DailyEntryDto> sorted = inputs.stream()
                 .filter(Objects::nonNull)
-                .sorted(Comparator.comparing(WeeklyReportEntryInputDto::date, Comparator.nullsLast(Comparator.naturalOrder())))
+                .sorted(Comparator.comparing(DailyEntryDto::date, Comparator.nullsLast(Comparator.naturalOrder())))
                 .toList();
 
         StringBuilder sb = new StringBuilder();
         int idx = 1;
 
-        for (WeeklyReportEntryInputDto e : sorted) {
+        for (DailyEntryDto e : sorted) {
             sb.append("- D").append(idx).append("(").append(valueOrNa(e.date() == null ? null : e.date().toString())).append(")\n")
                     .append("  question: ").append(valueOrNa(e.question())).append("\n")
                     .append("  answer: ").append(valueOrNa(e.answer())).append("\n")
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyReportGenerationListener.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/listener/WeeklyReportGenerationListener.java
similarity index 86%
rename from src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyReportGenerationListener.java
rename to src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/listener/WeeklyReportGenerationListener.java
index d7a09c4..f37a2e0 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/helper/WeeklyReportGenerationListener.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/application/listener/WeeklyReportGenerationListener.java
@@ -1,10 +1,11 @@
-package com.devkor.ifive.nadab.domain.weeklyreport.application.helper;
+package com.devkor.ifive.nadab.domain.weeklyreport.application.listener;
 
 import com.devkor.ifive.nadab.domain.weeklyreport.application.WeeklyReportTxService;
+import com.devkor.ifive.nadab.domain.weeklyreport.application.helper.WeeklyEntriesAssembler;
 import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.AiWeeklyReportResultDto;
-import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReportEntryInputDto;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
 import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReportGenerationRequestedEventDto;
-import com.devkor.ifive.nadab.domain.weeklyreport.core.infra.WeeklyReportLlmClient;
+import com.devkor.ifive.nadab.domain.weeklyreport.infra.WeeklyReportLlmClient;
 import com.devkor.ifive.nadab.domain.weeklyreport.core.repository.WeeklyQueryRepository;
 import com.devkor.ifive.nadab.global.shared.util.WeekRangeCalculator;
 import com.devkor.ifive.nadab.global.shared.util.dto.WeekRangeDto;
@@ -27,7 +28,7 @@ public class WeeklyReportGenerationListener {
     private final WeeklyReportLlmClient weeklyReportLlmClient;
     private final WeeklyReportTxService weeklyReportTxService;
 
-    private static final int MAX_LEN = 150;
+    private static final int MAX_LEN = 240;
 
     @Async("weeklyReportTaskExecutor")
     @TransactionalEventListener(phase =
@@ -36,7 +37,7 @@ public void handle(WeeklyReportGenerationRequestedEventDto event) {
 
         WeekRangeDto range = WeekRangeCalculator.getLastWeekRange();
 
-        List<WeeklyReportEntryInputDto> rows = weeklyQueryRepository.findWeeklyInputs(event.userId(), range.weekStartDate(), range.weekEndDate());
+        List<DailyEntryDto> rows = weeklyQueryRepository.findWeeklyInputs(event.userId(), range.weekStartDate(), range.weekEndDate());
         String entries = WeeklyEntriesAssembler.assemble(rows);
 
         AiWeeklyReportResultDto dto;
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/WeeklyReportEntryInputDto.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/DailyEntryDto.java
similarity index 87%
rename from src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/WeeklyReportEntryInputDto.java
rename to src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/DailyEntryDto.java
index e01ea88..224dd81 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/WeeklyReportEntryInputDto.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/dto/DailyEntryDto.java
@@ -4,7 +4,7 @@
 
 import java.time.LocalDate;
 
-public record WeeklyReportEntryInputDto(
+public record DailyEntryDto(
         LocalDate date,
         String question,
         String answer,
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyQueryRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyQueryRepository.java
index e053070..8b4391b 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyQueryRepository.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyQueryRepository.java
@@ -1,7 +1,7 @@
 package com.devkor.ifive.nadab.domain.weeklyreport.core.repository;
 
 import com.devkor.ifive.nadab.domain.dailyreport.core.entity.AnswerEntry;
-import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReportEntryInputDto;
+import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.query.Param;
@@ -15,7 +15,7 @@ public interface WeeklyQueryRepository extends Repository<AnswerEntry, Long> {
      * 주간 리포트 작성을 위한 입력 데이터 조회
      */
     @Query("""
-    select new com.devkor.ifive.nadab.domain.weeklyreport.core.dto.WeeklyReportEntryInputDto(
+    select new com.devkor.ifive.nadab.domain.weeklyreport.core.dto.DailyEntryDto(
         ae.date,
         dq.questionText,
         ae.content,
@@ -33,7 +33,7 @@ public interface WeeklyQueryRepository extends Repository<AnswerEntry, Long> {
     order by ae.date asc
 """)
 
-    List<WeeklyReportEntryInputDto> findWeeklyInputs(
+    List<DailyEntryDto> findWeeklyInputs(
             @Param("userId") Long userId,
             @Param("weekStart") LocalDate weekStart,
             @Param("weekEnd") LocalDate weekEnd
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyReportRepository.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyReportRepository.java
index f224ab2..a0c7ef4 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyReportRepository.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/repository/WeeklyReportRepository.java
@@ -8,6 +8,7 @@
 import org.springframework.data.repository.query.Param;
 
 import java.time.LocalDate;
+import java.util.List;
 import java.util.Optional;
 
 public interface WeeklyReportRepository extends JpaRepository<WeeklyReport, Long> {
@@ -62,4 +63,24 @@ int updateStatus(
             @Param("id") Long id,
             @Param("status") WeeklyReportStatus status
     );
+
+    /**
+     * 특정 월(monthStart ~ monthEnd)과 겹치는 주간 리포트 조회
+     * 월간 리포트 생성을 위해 사용
+     */
+    @Query("""
+        select wr
+        from WeeklyReport wr
+        where wr.user.id = :userId
+          and wr.weekStartDate <= :monthEnd
+          and wr.weekEndDate >= :monthStart
+          and wr.status = :status
+        order by wr.weekStartDate asc
+    """)
+    List<WeeklyReport> findMonthlyOverlappedWeeklyReports(
+            @Param("userId") Long userId,
+            @Param("monthStart") LocalDate monthStart,
+            @Param("monthEnd") LocalDate monthEnd,
+            @Param("status") WeeklyReportStatus status
+    );
 }
\ No newline at end of file
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/service/PendingWeeklyReportService.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/service/PendingWeeklyReportService.java
index 256c23c..4597e67 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/service/PendingWeeklyReportService.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/service/PendingWeeklyReportService.java
@@ -11,7 +11,6 @@
 import com.devkor.ifive.nadab.global.shared.util.dto.WeekRangeDto;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
-import org.springframework.transaction.annotation.Propagation;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.time.LocalDate;
diff --git a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/infra/WeeklyReportLlmClient.java b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/infra/WeeklyReportLlmClient.java
similarity index 96%
rename from src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/infra/WeeklyReportLlmClient.java
rename to src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/infra/WeeklyReportLlmClient.java
index fd53a51..d666b44 100644
--- a/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/core/infra/WeeklyReportLlmClient.java
+++ b/src/main/java/com/devkor/ifive/nadab/domain/weeklyreport/infra/WeeklyReportLlmClient.java
@@ -1,4 +1,4 @@
-package com.devkor.ifive.nadab.domain.weeklyreport.core.infra;
+package com.devkor.ifive.nadab.domain.weeklyreport.infra;
 
 import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.AiWeeklyReportResultDto;
 import com.devkor.ifive.nadab.domain.weeklyreport.core.dto.LlmWeeklyResultDto;
@@ -34,7 +34,7 @@ public AiWeeklyReportResultDto generate(String weekStartDate, String weekEndDate
 
         OpenAiChatOptions options = OpenAiChatOptions.builder()
                 .model(OpenAiApi.ChatModel.GPT_5_MINI)
-                .reasoningEffort("low")
+                .reasoningEffort("medium")
                 .temperature(1.0)
                 .build();
 
diff --git a/src/main/java/com/devkor/ifive/nadab/global/core/config/infra/AsyncConfig.java b/src/main/java/com/devkor/ifive/nadab/global/core/config/infra/AsyncConfig.java
index 000dd13..074aafc 100644
--- a/src/main/java/com/devkor/ifive/nadab/global/core/config/infra/AsyncConfig.java
+++ b/src/main/java/com/devkor/ifive/nadab/global/core/config/infra/AsyncConfig.java
@@ -55,4 +55,19 @@ public ThreadPoolTaskExecutor weeklyReportTaskExecutor() {
         executor.initialize();
         return executor;
     }
+
+    /**
+     * 월간 리포트(LLM 호출) 전용 실행기
+     * - LLM은 외부 I/O라 동시성 높게 주되, 무한 큐 적체는 막기 위해 큐 제한
+     */
+    @Bean(name = "monthlyReportTaskExecutor")
+    public ThreadPoolTaskExecutor monthlyReportTaskExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(4);
+        executor.setMaxPoolSize(8);
+        executor.setQueueCapacity(50);
+        executor.setThreadNamePrefix("async-monthly-report-");
+        executor.initialize();
+        return executor;
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/LocalMonthlyReportPromptLoader.java b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/LocalMonthlyReportPromptLoader.java
new file mode 100644
index 0000000..d500040
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/LocalMonthlyReportPromptLoader.java
@@ -0,0 +1,38 @@
+package com.devkor.ifive.nadab.global.core.prompt.monthly;
+
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.BadRequestException;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.annotation.Profile;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+@Component
+@Profile("local")
+@Slf4j
+public class LocalMonthlyReportPromptLoader implements MonthlyReportPromptLoader {
+
+    private static final String PROMPT_PATH = "secret/monthly-prompt-local.txt";
+
+    @Override
+    public String loadPrompt() {
+        try {
+            ClassPathResource resource = new ClassPathResource(PROMPT_PATH);
+
+            if (!resource.exists()) {
+                log.error("월간 리포트 프롬프트 파일이 존재하지 않습니다: {}", PROMPT_PATH);
+                throw new BadRequestException(ErrorCode.PROMPT_MONTHLY_FILE_NOT_FOUND);
+            }
+
+            byte[] bytes = resource.getContentAsByteArray();
+            return new String(bytes, StandardCharsets.UTF_8);
+
+        } catch (IOException e) {
+            log.error("로컬 월간 리포트 프롬프트 파일 읽기 실패: {}", PROMPT_PATH, e);
+            throw new BadRequestException(ErrorCode.PROMPT_MONTHLY_FILE_READ_FAILED);
+        }
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/MonthlyReportPromptLoader.java b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/MonthlyReportPromptLoader.java
new file mode 100644
index 0000000..2092eba
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/MonthlyReportPromptLoader.java
@@ -0,0 +1,5 @@
+package com.devkor.ifive.nadab.global.core.prompt.monthly;
+
+public interface MonthlyReportPromptLoader {
+    String loadPrompt();
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/SecretMonthlyReportPromptLoader.java b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/SecretMonthlyReportPromptLoader.java
new file mode 100644
index 0000000..d48e4af
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/core/prompt/monthly/SecretMonthlyReportPromptLoader.java
@@ -0,0 +1,29 @@
+package com.devkor.ifive.nadab.global.core.prompt.monthly;
+
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.BadRequestException;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Component;
+
+@Component
+@Profile("dev")
+@Slf4j
+@RequiredArgsConstructor
+public class SecretMonthlyReportPromptLoader implements MonthlyReportPromptLoader {
+
+    @Value("${MONTHLY_PROMPT}")
+    private String rawPrompt;
+
+    @Override
+    public String loadPrompt() {
+        if (rawPrompt == null || rawPrompt.isBlank()) {
+            log.error("환경 변수 MONTHLY_PROMPT가 비어있습니다.");
+            throw new BadRequestException(ErrorCode.PROMPT_MONTHLY_ENV_VAR_NOT_SET);
+        }
+
+        return rawPrompt;
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/global/core/response/ErrorCode.java b/src/main/java/com/devkor/ifive/nadab/global/core/response/ErrorCode.java
index c6acc5b..3295249 100644
--- a/src/main/java/com/devkor/ifive/nadab/global/core/response/ErrorCode.java
+++ b/src/main/java/com/devkor/ifive/nadab/global/core/response/ErrorCode.java
@@ -133,6 +133,18 @@ public enum ErrorCode {
     WEEKLY_REPORT_ALREADY_COMPLETED(HttpStatus.CONFLICT, "이미 작성된 주간 리포트가 존재합니다"),
     WEEKLY_REPORT_IN_PROGRESS(HttpStatus.CONFLICT, "현재 주간 리포트를 생성 중입니다"),
 
+    // ==================== MONTHLY_REPORT (월간 리포트) ====================
+    // 400 Bad Request
+    MONTHLY_REPORT_NOT_ENOUGH_REPORTS(HttpStatus.BAD_REQUEST, "월간 리포트 작성 자격이 없습니다. (지난 달 15회 이상 완료 필요)"),
+
+    // 404 Not Found
+    MONTHLY_REPORT_NOT_FOUND(HttpStatus.NOT_FOUND, "월간 리포트를 찾을 수 없습니다"),
+    MONTHLY_REPORT_NOT_COMPLETED(HttpStatus.NOT_FOUND, "해당 월간 리포트가 아직 생성 완료되지 않았습니다"),
+
+    // 409 Conflict
+    MONTHLY_REPORT_ALREADY_COMPLETED(HttpStatus.CONFLICT, "이미 작성된 월간 리포트가 존재합니다"),
+    MONTHLY_REPORT_IN_PROGRESS(HttpStatus.CONFLICT, "현재 월간 리포트를 생성 중입니다"),
+
     // ==================== AI (인공지능) ====================
     // 502 Bad Gateway
     AI_RESPONSE_PARSE_FAILED(HttpStatus.BAD_GATEWAY, "AI 응답 형식을 해석할 수 없습니다"),
@@ -164,10 +176,15 @@ public enum ErrorCode {
     PROMPT_DAILY_FILE_NOT_FOUND(HttpStatus.BAD_REQUEST, "일간 리포트 프롬프트 파일이 존재하지 않습니다"),
     PROMPT_DAILY_FILE_READ_FAILED(HttpStatus.BAD_REQUEST, "로컬 일간 리포트 프롬프트 파일을 읽을 수 없습니다"),
     PROMPT_DAILY_ENV_VAR_NOT_SET(HttpStatus.BAD_REQUEST, "INSIGHT_PROMPT 환경 변수에 프롬프트가 설정되어 있지 않습니다"),
+
     PROMPT_WEEKLY_FILE_NOT_FOUND(HttpStatus.BAD_REQUEST, "주간 리포트 프롬프트 파일이 존재하지 않습니다"),
     PROMPT_WEEKLY_FILE_READ_FAILED(HttpStatus.BAD_REQUEST, "로컬 주간 리포트 프롬프트 파일을 읽을 수 없습니다"),
     PROMPT_WEEKLY_ENV_VAR_NOT_SET(HttpStatus.BAD_REQUEST, "WEEKLY_PROMPT 환경 변수에 프롬프트가 설정되어 있지 않습니다"),
 
+    PROMPT_MONTHLY_FILE_NOT_FOUND(HttpStatus.BAD_REQUEST, "월간 리포트 프롬프트 파일이 존재하지 않습니다"),
+    PROMPT_MONTHLY_FILE_READ_FAILED(HttpStatus.BAD_REQUEST, "로컬 월간 리포트 프롬프트 파일을 읽을 수 없습니다"),
+    PROMPT_MONTHLY_ENV_VAR_NOT_SET(HttpStatus.BAD_REQUEST, "MONTHLY_PROMPT 환경 변수에 프롬프트가 설정되어 있지 않습니다"),
+
     // ==================== NICKNAME (닉네임) ====================
     // 400 Bad Request
     NICKNAME_CHANGE_LIMIT_EXCEEDED(HttpStatus.BAD_REQUEST, "닉네임 변경 가능 횟수를 초과했습니다 (14일 내 최대 2회)");
diff --git a/src/main/java/com/devkor/ifive/nadab/global/exception/ExceptionController.java b/src/main/java/com/devkor/ifive/nadab/global/exception/ExceptionController.java
index 9696525..e50e715 100644
--- a/src/main/java/com/devkor/ifive/nadab/global/exception/ExceptionController.java
+++ b/src/main/java/com/devkor/ifive/nadab/global/exception/ExceptionController.java
@@ -7,6 +7,7 @@
 import com.devkor.ifive.nadab.global.core.response.ErrorCode;
 import com.devkor.ifive.nadab.global.exception.ai.AiResponseParseException;
 import com.devkor.ifive.nadab.global.exception.ai.AiServiceUnavailableException;
+import com.devkor.ifive.nadab.global.exception.report.MonthlyReportNotEligibleException;
 import com.devkor.ifive.nadab.global.exception.report.WeeklyReportNotEligibleException;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.http.ResponseEntity;
@@ -116,6 +117,12 @@ public ResponseEntity<ApiErrorResponseDto<CompletedCountResponse>> handleWeeklyR
         return ApiResponseEntity.error(ex.getErrorCode(), ex.getCompletedCountResponse());
     }
 
+    @ExceptionHandler(MonthlyReportNotEligibleException.class)
+    public ResponseEntity<ApiErrorResponseDto<CompletedCountResponse>> handleMonthlyReportNotEligibleException(MonthlyReportNotEligibleException ex) {
+        log.warn("MonthlyReportNotEligibleException: {}", ex.getMessage(), ex);
+        return ApiResponseEntity.error(ex.getErrorCode(), ex.getCompletedCountResponse());
+    }
+
     @ExceptionHandler(RuntimeException.class)
     public ResponseEntity<ApiErrorResponseDto<Void>> handleRuntimeException(RuntimeException ex) {
         if (ex instanceof AuthenticationException || ex instanceof AccessDeniedException) {
diff --git a/src/main/java/com/devkor/ifive/nadab/global/exception/report/MonthlyReportNotEligibleException.java b/src/main/java/com/devkor/ifive/nadab/global/exception/report/MonthlyReportNotEligibleException.java
new file mode 100644
index 0000000..b2ad00d
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/exception/report/MonthlyReportNotEligibleException.java
@@ -0,0 +1,16 @@
+package com.devkor.ifive.nadab.global.exception.report;
+
+import com.devkor.ifive.nadab.domain.weeklyreport.api.dto.response.CompletedCountResponse;
+import com.devkor.ifive.nadab.global.core.response.ErrorCode;
+import com.devkor.ifive.nadab.global.exception.BadRequestException;
+import lombok.Getter;
+
+@Getter
+public class MonthlyReportNotEligibleException extends BadRequestException {
+    private final CompletedCountResponse completedCountResponse;
+
+    public MonthlyReportNotEligibleException(ErrorCode errorCode, CompletedCountResponse completedCount) {
+        super(errorCode);
+        this.completedCountResponse = completedCount;
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/global/shared/util/MonthRangeCalculator.java b/src/main/java/com/devkor/ifive/nadab/global/shared/util/MonthRangeCalculator.java
new file mode 100644
index 0000000..db7be2e
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/shared/util/MonthRangeCalculator.java
@@ -0,0 +1,42 @@
+package com.devkor.ifive.nadab.global.shared.util;
+
+import com.devkor.ifive.nadab.global.shared.util.dto.MonthRangeDto;
+
+import java.time.LocalDate;
+import java.time.YearMonth;
+import java.time.ZoneId;
+
+public final class MonthRangeCalculator {
+
+    private static final ZoneId KST = ZoneId.of("Asia/Seoul");
+
+    private MonthRangeCalculator() {
+    }
+
+    /**
+     * 주어진 날짜가 속한 월(1일 ~ 말일) 범위를 반환합니다.
+     */
+    public static MonthRangeDto monthRangeOf(LocalDate date) {
+        YearMonth ym = YearMonth.from(date);
+        LocalDate start = ym.atDay(1);
+        LocalDate end = ym.atEndOfMonth();
+        return new MonthRangeDto(start, end);
+    }
+
+    /**
+     * KST 기준 "저번 달" 범위를 반환합니다.
+     */
+    public static MonthRangeDto getLastMonthRange() {
+        LocalDate today = LocalDate.now(KST);
+        LocalDate lastMonthDate = today.minusMonths(1);
+        return monthRangeOf(lastMonthDate);
+    }
+
+    /**
+     * KST 기준 "이번 달" 범위를 반환합니다.
+     */
+    public static MonthRangeDto getThisMonthRange() {
+        LocalDate today = LocalDate.now(KST);
+        return monthRangeOf(today);
+    }
+}
diff --git a/src/main/java/com/devkor/ifive/nadab/global/shared/util/dto/MonthRangeDto.java b/src/main/java/com/devkor/ifive/nadab/global/shared/util/dto/MonthRangeDto.java
new file mode 100644
index 0000000..1b8b065
--- /dev/null
+++ b/src/main/java/com/devkor/ifive/nadab/global/shared/util/dto/MonthRangeDto.java
@@ -0,0 +1,9 @@
+package com.devkor.ifive.nadab.global.shared.util.dto;
+
+import java.time.LocalDate;
+
+public record MonthRangeDto(
+        LocalDate monthStartDate,
+        LocalDate monthEndDate
+) {
+}
diff --git a/src/main/resources/db/migration/V20260110_1638__IS_create_monthly_reports_table.sql b/src/main/resources/db/migration/V20260110_1638__IS_create_monthly_reports_table.sql
new file mode 100644
index 0000000..a31f40e
--- /dev/null
+++ b/src/main/resources/db/migration/V20260110_1638__IS_create_monthly_reports_table.sql
@@ -0,0 +1,26 @@
+CREATE TABLE monthly_reports (
+                                 id BIGSERIAL PRIMARY KEY,
+                                 user_id BIGINT NOT NULL,
+
+                                 month_start_date DATE NOT NULL,
+                                 month_end_date   DATE NOT NULL,
+
+                                 discovered VARCHAR(250),
+                                 good       VARCHAR(250),
+                                 improve    VARCHAR(250),
+
+                                 status VARCHAR(16) NOT NULL,
+                                 date   DATE NOT NULL,
+                                 analyzed_at TIMESTAMPTZ,
+
+                                 created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+
+                                 CONSTRAINT fk_monthly_reports_user
+                                     FOREIGN KEY (user_id) REFERENCES users(id),
+
+                                 CONSTRAINT uq_monthly_reports_user_month
+                                     UNIQUE (user_id, month_start_date)
+);
+
+CREATE INDEX idx_monthly_reports_user_month_start
+    ON monthly_reports(user_id, month_start_date DESC);
\ No newline at end of file