diff --git a/src/app/api/auth/token/login/route.ts b/src/app/api/auth/token/login/route.ts
index f95d343..f5f7c42 100644
--- a/src/app/api/auth/token/login/route.ts
+++ b/src/app/api/auth/token/login/route.ts
@@ -7,12 +7,25 @@ import { NextRequest, NextResponse } from 'next/server';
 import { prisma } from '@/lib/db';
 import { generateAccessToken, generateRefreshToken } from '@/lib/utils/jwt';
 import { RMABLogger } from '@/lib/utils/logger';
+import { checkTokenLoginRateLimit } from '@/lib/utils/authRateLimit';
 import crypto from 'crypto';
 
 const logger = RMABLogger.create('API.Auth.TokenLogin');
 
 export async function POST(request: NextRequest) {
   try {
+    const ip = request.headers.get('x-forwarded-for') ?? 'unknown';
+    const rateLimit = checkTokenLoginRateLimit(ip);
+    if (!rateLimit.allowed) {
+      return NextResponse.json(
+        { error: 'Too many login attempts. Please try again later.' },
+        {
+          status: 429,
+          headers: { 'Retry-After': String(rateLimit.retryAfterSeconds) },
+        }
+      );
+    }
+
     const { token } = await request.json();
 
     if (!token) {
diff --git a/src/lib/utils/authRateLimit.ts b/src/lib/utils/authRateLimit.ts
new file mode 100644
index 0000000..0d0a56c
--- /dev/null
+++ b/src/lib/utils/authRateLimit.ts
@@ -0,0 +1,89 @@
+/**
+ * Component: Auth Rate Limiting
+ * Documentation: documentation/backend/services/auth.md
+ *
+ * In-memory fixed-window rate limiter with lazy eviction and periodic sweep
+ * to prevent unbounded memory growth.
+ */
+
+type Bucket = {
+  count: number;
+  resetAt: number;
+};
+
+type RateLimitResult = {
+  allowed: boolean;
+  retryAfterSeconds: number;
+};
+
+const buckets = new Map<string, Bucket>();
+
+/** Number of checkRateLimit calls since the last full sweep */
+let checkCount = 0;
+
+/** How often (in calls) to perform a full sweep of expired buckets */
+const SWEEP_INTERVAL = 100;
+
+/**
+ * Sweep the entire bucket map and delete all expired entries.
+ * Called automatically every SWEEP_INTERVAL checks.
+ */
+function sweepExpiredBuckets(): void {
+  const now = Date.now();
+  for (const [key, bucket] of buckets) {
+    if (now >= bucket.resetAt) {
+      buckets.delete(key);
+    }
+  }
+}
+
+function checkRateLimit(key: string, maxRequests: number, windowMs: number): RateLimitResult {
+  const now = Date.now();
+
+  // Periodic full sweep every SWEEP_INTERVAL calls
+  checkCount += 1;
+  if (checkCount >= SWEEP_INTERVAL) {
+    checkCount = 0;
+    sweepExpiredBuckets();
+  }
+
+  const current = buckets.get(key);
+
+  // Lazy eviction: if the bucket is expired, delete it and start fresh
+  if (!current || now >= current.resetAt) {
+    if (current) {
+      buckets.delete(key);
+    }
+    buckets.set(key, { count: 1, resetAt: now + windowMs });
+    return { allowed: true, retryAfterSeconds: Math.ceil(windowMs / 1000) };
+  }
+
+  if (current.count >= maxRequests) {
+    return {
+      allowed: false,
+      retryAfterSeconds: Math.max(1, Math.ceil((current.resetAt - now) / 1000)),
+    };
+  }
+
+  current.count += 1;
+  return {
+    allowed: true,
+    retryAfterSeconds: Math.max(1, Math.ceil((current.resetAt - now) / 1000)),
+  };
+}
+
+/** 10 attempts per 15 minutes per IP */
+export function checkTokenLoginRateLimit(ip: string): RateLimitResult {
+  return checkRateLimit(`token-login:${ip}`, 10, 15 * 60 * 1000);
+}
+
+/** Reset all buckets and the sweep counter. For testing only. */
+export function _resetBuckets(): void {
+  buckets.clear();
+  checkCount = 0;
+}
+
+/** Get the current number of tracked buckets. For testing only. */
+export function _getBucketCount(): number {
+  return buckets.size;
+}
diff --git a/tests/api/auth-login-token.routes.test.ts b/tests/api/auth-login-token.routes.test.ts
index c72a2eb..12015a7 100644
--- a/tests/api/auth-login-token.routes.test.ts
+++ b/tests/api/auth-login-token.routes.test.ts
@@ -9,6 +9,7 @@ import { createPrismaMock } from '../helpers/prisma';
 const prismaMock = createPrismaMock();
 const generateAccessTokenMock = vi.hoisted(() => vi.fn());
 const generateRefreshTokenMock = vi.hoisted(() => vi.fn());
+const checkTokenLoginRateLimitMock = vi.hoisted(() => vi.fn());
 
 vi.mock('@/lib/db', () => ({
   prisma: prismaMock,
@@ -19,11 +20,23 @@ vi.mock('@/lib/utils/jwt', () => ({
   generateRefreshToken: generateRefreshTokenMock,
 }));
 
+vi.mock('@/lib/utils/authRateLimit', () => ({
+  checkTokenLoginRateLimit: checkTokenLoginRateLimitMock,
+}));
+
+function makeRequest(body: Record<string, unknown>, ip = '127.0.0.1') {
+  return {
+    headers: { get: vi.fn().mockReturnValue(ip) },
+    json: vi.fn().mockResolvedValue(body),
+  };
+}
+
 describe('POST /api/auth/token/login', () => {
   beforeEach(() => {
     vi.clearAllMocks();
     generateAccessTokenMock.mockReturnValue('access-token');
     generateRefreshTokenMock.mockReturnValue('refresh-token');
+    checkTokenLoginRateLimitMock.mockReturnValue({ allowed: true, retryAfterSeconds: 900 });
   });
 
   it('authenticates user with a valid token', async () => {
@@ -38,8 +51,7 @@ describe('POST /api/auth/token/login', () => {
     prismaMock.user.update.mockResolvedValueOnce({});
 
     const { POST } = await import('@/app/api/auth/token/login/route');
-    const request = { json: vi.fn().mockResolvedValue({ token: 'rmab_valid_token' }) };
-    const response = await POST(request as any);
+    const response = await POST(makeRequest({ token: 'rmab_valid_token' }) as any);
     const payload = await response.json();
 
     expect(response.status).toBe(200);
@@ -51,8 +63,7 @@ describe('POST /api/auth/token/login', () => {
 
   it('returns 400 when token parameter is missing', async () => {
     const { POST } = await import('@/app/api/auth/token/login/route');
-    const request = { json: vi.fn().mockResolvedValue({}) };
-    const response = await POST(request as any);
+    const response = await POST(makeRequest({}) as any);
     const payload = await response.json();
 
     expect(response.status).toBe(400);
@@ -63,11 +74,22 @@ describe('POST /api/auth/token/login', () => {
     prismaMock.user.findFirst.mockResolvedValueOnce(null);
 
     const { POST } = await import('@/app/api/auth/token/login/route');
-    const request = { json: vi.fn().mockResolvedValue({ token: 'rmab_invalid' }) };
-    const response = await POST(request as any);
+    const response = await POST(makeRequest({ token: 'rmab_invalid' }) as any);
     const payload = await response.json();
 
     expect(response.status).toBe(401);
     expect(payload.error).toMatch(/Invalid token/);
   });
+
+  it('returns 429 when rate limit is exceeded', async () => {
+    checkTokenLoginRateLimitMock.mockReturnValue({ allowed: false, retryAfterSeconds: 600 });
+
+    const { POST } = await import('@/app/api/auth/token/login/route');
+    const response = await POST(makeRequest({ token: 'rmab_any' }) as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(429);
+    expect(payload.error).toMatch(/Too many login attempts/);
+    expect(response.headers.get('Retry-After')).toBe('600');
+  });
 });