diff --git a/backend/src/modules/auth/auth.service.spec.ts b/backend/src/modules/auth/auth.service.spec.ts
index 15d8910..b34ebc3 100644
--- a/backend/src/modules/auth/auth.service.spec.ts
+++ b/backend/src/modules/auth/auth.service.spec.ts
@@ -7,10 +7,15 @@ import { ConfigService } from '@nestjs/config';
 import { getRepositoryToken } from '@nestjs/typeorm';
 import { RefreshToken } from './refresh-token.entity';
 import { PasswordReset } from './password-reset.entity';
-import { BadRequestException, NotFoundException } from '@nestjs/common';
+import {
+  BadRequestException,
+  NotFoundException,
+  UnauthorizedException,
+} from '@nestjs/common';
 import * as bcrypt from 'bcrypt';
+import * as crypto from 'crypto';
 
-describe('AuthService - Password Reset', () => {
+describe('AuthService', () => {
   let service: AuthService;
 
   const mockUser = {
@@ -342,4 +347,111 @@ describe('AuthService - Password Reset', () => {
       expect(matches).toBe(true);
     });
   });
+
+  describe('refresh token hashing', () => {
+    function sha256(raw: string): string {
+      return crypto.createHash('sha256').update(raw).digest('hex');
+    }
+
+    describe('generateRefreshToken', () => {
+      it('should return the raw token, not the hash', async () => {
+        mockRefreshTokenRepository.save.mockResolvedValue({});
+
+        const raw = await service.generateRefreshToken(mockUser.id);
+
+        // 32 random bytes encoded as hex = 64 chars
+        expect(raw).toMatch(/^[0-9a-f]{64}$/);
+      });
+
+      it('should persist the SHA-256 hash, not the raw token', async () => {
+        let savedData: any;
+        mockRefreshTokenRepository.save.mockImplementation((data) => {
+          savedData = data;
+          return Promise.resolve(data);
+        });
+
+        const raw = await service.generateRefreshToken(mockUser.id);
+
+        expect(savedData.token).toBe(sha256(raw));
+        expect(savedData.token).not.toBe(raw);
+      });
+
+      it('should set expiry 7 calendar days from now', async () => {
+        const now = new Date();
+        let savedData: any;
+        mockRefreshTokenRepository.save.mockImplementation((data) => {
+          savedData = data;
+          return Promise.resolve(data);
+        });
+
+        await service.generateRefreshToken(mockUser.id);
+
+        // Mirror the implementation's setDate(+7) so the assertion is
+        // DST-safe (calendar days ≠ exactly 7 * 24h across DST boundaries).
+        const expected = new Date(now);
+        expected.setDate(expected.getDate() + 7);
+        expect(
+          Math.abs(savedData.expiresAt.getTime() - expected.getTime()),
+        ).toBeLessThan(1000);
+      });
+    });
+
+    describe('refreshAccessToken', () => {
+      it('should query the repository using the SHA-256 hash of the presented token', async () => {
+        const rawToken = 'a'.repeat(64);
+        const storedToken = {
+          id: '550e8400-e29b-41d4-a716-446655440001',
+          token: sha256(rawToken),
+          revoked: false,
+          expiresAt: new Date(Date.now() + 7 * 24 * 60 * 60 * 1000),
+          user: mockUser,
+          userId: mockUser.id,
+        };
+
+        mockRefreshTokenRepository.findOne.mockResolvedValue(storedToken);
+        mockRefreshTokenRepository.update.mockResolvedValue({ affected: 1 });
+        mockRefreshTokenRepository.save.mockResolvedValue({});
+        mockJwtService.sign.mockReturnValue('new-access-token');
+
+        await service.refreshAccessToken(rawToken);
+
+        expect(mockRefreshTokenRepository.findOne).toHaveBeenCalledWith(
+          expect.objectContaining({ where: { token: sha256(rawToken) } }),
+        );
+      });
+
+      it('should reject a token that has no matching hash in the database', async () => {
+        mockRefreshTokenRepository.findOne.mockResolvedValue(null);
+
+        await expect(
+          service.refreshAccessToken('plaintext-token'),
+        ).rejects.toThrow(UnauthorizedException);
+      });
+    });
+
+    describe('revokeRefreshToken', () => {
+      it('should update using the SHA-256 hash of the presented token', async () => {
+        const rawToken = 'b'.repeat(64);
+        mockRefreshTokenRepository.update.mockResolvedValue({ affected: 1 });
+
+        await service.revokeRefreshToken(rawToken);
+
+        expect(mockRefreshTokenRepository.update).toHaveBeenCalledWith(
+          { token: sha256(rawToken) },
+          { revoked: true },
+        );
+      });
+
+      it('should not pass the raw token to the repository', async () => {
+        const rawToken = 'plaintext-token';
+        mockRefreshTokenRepository.update.mockResolvedValue({ affected: 0 });
+
+        await service.revokeRefreshToken(rawToken);
+
+        const callArg = mockRefreshTokenRepository.update.mock.calls[0][0];
+        expect(callArg.token).toBe(sha256(rawToken));
+        expect(callArg.token).not.toBe(rawToken);
+      });
+    });
+  });
 });
diff --git a/backend/src/modules/auth/auth.service.ts b/backend/src/modules/auth/auth.service.ts
index 2917db2..23f03ca 100644
--- a/backend/src/modules/auth/auth.service.ts
+++ b/backend/src/modules/auth/auth.service.ts
@@ -79,31 +79,31 @@ export class AuthService {
     return result;
   }
 
+  private hashToken(raw: string): string {
+    return crypto.createHash('sha256').update(raw).digest('hex');
+  }
+
   async generateRefreshToken(userId: number): Promise<string> {
-    // Generate a random token
-    const token = crypto.randomBytes(32).toString('hex');
+    const raw = crypto.randomBytes(32).toString('hex');
 
-    // Calculate expiry (7 days from now)
     const expiresAt = new Date();
     expiresAt.setDate(expiresAt.getDate() + 7);
 
-    // Save to database
     await this.refreshTokenRepository.save({
-      token,
+      token: this.hashToken(raw),
       userId,
       expiresAt,
       revoked: false,
     });
 
-    return token;
+    return raw;
   }
 
   async refreshAccessToken(
     refreshToken: string,
   ): Promise<{ access_token: string; refresh_token: string }> {
-    // Find the refresh token
     const storedToken = await this.refreshTokenRepository.findOne({
-      where: { token: refreshToken },
+      where: { token: this.hashToken(refreshToken) },
       relations: ['user'],
     });
 
@@ -111,7 +111,6 @@ export class AuthService {
       throw new UnauthorizedException('Invalid refresh token');
     }
 
-    // Check if token is expired or revoked
     if (storedToken.revoked || new Date() > storedToken.expiresAt) {
       throw new UnauthorizedException('Refresh token expired or revoked');
     }
@@ -121,7 +120,6 @@ export class AuthService {
       revoked: true,
     });
 
-    // Generate new tokens
     const payload = {
       username: storedToken.user.username,
       sub: storedToken.user.id,
@@ -138,7 +136,10 @@ export class AuthService {
   }
 
   async revokeRefreshToken(token: string): Promise<void> {
-    await this.refreshTokenRepository.update({ token }, { revoked: true });
+    await this.refreshTokenRepository.update(
+      { token: this.hashToken(token) },
+      { revoked: true },
+    );
   }
 
   async requestPasswordReset(email: string): Promise<{ message: string }> {