diff --git a/server/index.js b/server/index.js
index f5cc645..10a19cd 100644
--- a/server/index.js
+++ b/server/index.js
@@ -18,7 +18,14 @@ import feedbackRoutes from "./routes/feedback.js";
 import pdfChatRoutes from "./routes/pdfChat.js";
 import sitemapRoutes from "./routes/sitemap.js";
 import { setupSocketHandlers } from "./socket/socketHandlers.js";
-import initRedis from "./utils/redis.js";
+import {
+  generalLimiter,
+  authLimiter,
+  uploadLimiter,
+  discussionLimiter,
+  chatLimiter,
+  strictAuthLimiter,
+} from "./middleware/rateLimiter.js";
 
 BigInt.prototype.toJSON = function () {
   return this.toString();
@@ -27,14 +34,6 @@ BigInt.prototype.toJSON = function () {
 // Load environment variables
 dotenv.config();
 
-// Initialize Redis (optional - will work without it)
-initRedis().catch((err) => {
-  console.log(
-    "⚠️  Redis not available, continuing without cache:",
-    err.message
-  );
-});
-
 const app = express();
 const server = createServer(app);
 
@@ -78,6 +77,21 @@ app.use(express.urlencoded({ extended: true, limit: "50mb" }));
 // Initialize Passport
 app.use(passport.initialize());
 
+// Rate Limiting Middleware
+app.use("/api/", generalLimiter);
+app.use("/api/auth/login", authLimiter);
+app.use("/api/auth/send-otp", authLimiter);
+app.use("/api/auth/forgot-password", strictAuthLimiter);
+app.use("/api/auth/reset-password", strictAuthLimiter);
+app.use("/api/upload", uploadLimiter);
+app.use("/api/discussions", (req, res, next) => {
+  if (["POST"].includes(req.method)) {
+    return discussionLimiter(req, res, next);
+  }
+  next();
+});
+app.use("/api/pdf-chat", chatLimiter);
+
 // Debug middleware to log all requests
 app.use((req, res, next) => {
   console.log(`🔍 ${req.method} ${req.path}`);
@@ -107,7 +121,7 @@ app.use("/", sitemapRoutes);
 // Setup Socket.IO handlers
 setupSocketHandlers(io);
 
-// Health check endpoint
+// Health check endpoint (not rate limited)
 app.get("/api/health", async (req, res) => {
   try {
     // Test database connection
diff --git a/server/middleware/rateLimiter.js b/server/middleware/rateLimiter.js
new file mode 100644
index 0000000..c146970
--- /dev/null
+++ b/server/middleware/rateLimiter.js
@@ -0,0 +1,159 @@
+import rateLimit from "express-rate-limit";
+
+// General API Rate Limit: 500 requests per 15 minutes per IP
+export const generalLimiter = rateLimit({
+  windowMs: 15 * 60 * 1000,
+  max: 500,
+  message: {
+    error: "Too many requests from this IP, please try again later.",
+    retryAfter: "15 minutes",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  skip: (req) => req.path === "/api/health",
+  keyGenerator: (req) =>
+    req.headers["x-forwarded-for"]?.split(",")[0] ||
+    req.socket.remoteAddress ||
+    "unknown",
+});
+
+// Authentication Rate Limit: 5 login attempts per 15 minutes per IP
+export const authLimiter = rateLimit({
+  windowMs: 15 * 60 * 1000,
+  max: 5,
+  message: {
+    error: "Too many login attempts, please try again after 15 minutes.",
+    retryAfter: "15 minutes",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  skip: (req) => req.path.includes("signup") && req.method === "POST",
+  keyGenerator: (req) =>
+    req.headers["x-forwarded-for"]?.split(",")[0] ||
+    req.socket.remoteAddress ||
+    "unknown",
+});
+
+// File Upload Rate Limit: 10 uploads per hour per authenticated user
+export const uploadLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 10,
+  message: {
+    error: "Upload limit exceeded. Maximum 10 files per hour.",
+    retryAfter: "1 hour",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req) => {
+    if (req.user && req.user.id) {
+      return `upload_${req.user.id}`;
+    }
+    return `upload_${
+      req.headers["x-forwarded-for"]?.split(",")[0] ||
+      req.socket.remoteAddress ||
+      "unknown"
+    }`;
+  },
+  handler: (req, res) => {
+    res.status(429).json({
+      error: "Upload limit exceeded. Maximum 10 files per hour.",
+      retryAfter: "1 hour",
+    });
+  },
+});
+
+// Discussion/Comment Rate Limit: 20 posts per hour per authenticated user
+export const discussionLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 20,
+  message: {
+    error: "Discussion posting limit exceeded. Maximum 20 posts per hour.",
+    retryAfter: "1 hour",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req) => {
+    if (req.user && req.user.id) {
+      return `discussion_${req.user.id}`;
+    }
+    return `discussion_${
+      req.headers["x-forwarded-for"]?.split(",")[0] ||
+      req.socket.remoteAddress ||
+      "unknown"
+    }`;
+  },
+  handler: (req, res) => {
+    res.status(429).json({
+      error: "Discussion posting limit exceeded. Maximum 20 posts per hour.",
+      retryAfter: "1 hour",
+    });
+  },
+});
+
+// AI Chat Rate Limit: 30 requests per hour per authenticated user
+export const chatLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 30,
+  message: {
+    error: "Chat limit exceeded. Maximum 30 messages per hour.",
+    retryAfter: "1 hour",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req) => {
+    if (req.user && req.user.id) {
+      return `chat_${req.user.id}`;
+    }
+    return `chat_${
+      req.headers["x-forwarded-for"]?.split(",")[0] ||
+      req.socket.remoteAddress ||
+      "unknown"
+    }`;
+  },
+  handler: (req, res) => {
+    res.status(429).json({
+      error: "Chat limit exceeded. Maximum 30 messages per hour.",
+      retryAfter: "1 hour",
+    });
+  },
+});
+
+// Password Reset Rate Limit: 3 attempts per hour per email/IP
+export const strictAuthLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 3,
+  message: {
+    error: "Too many password reset attempts. Please try again after 1 hour.",
+    retryAfter: "1 hour",
+  },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req) => {
+    const email = req.body?.email || req.query?.email;
+    if (email) {
+      return `passwordreset_${email.toLowerCase()}`;
+    }
+    return `passwordreset_${
+      req.headers["x-forwarded-for"]?.split(",")[0] ||
+      req.socket.remoteAddress ||
+      "unknown"
+    }`;
+  },
+  handler: (req, res) => {
+    res.status(429).json({
+      error: "Too many password reset attempts. Please try again after 1 hour.",
+      retryAfter: "1 hour",
+    });
+  },
+});
+
+// Custom rate limiter factory for fine-grained control
+export const createCustomLimiter = (options = {}) => {
+  const defaults = {
+    windowMs: 15 * 60 * 1000,
+    max: 500,
+    standardHeaders: true,
+    legacyHeaders: false,
+  };
+  return rateLimit({ ...defaults, ...options });
+};
diff --git a/server/package.json b/server/package.json
index df81ad1..73ebd5f 100644
--- a/server/package.json
+++ b/server/package.json
@@ -22,6 +22,7 @@
     "cors": "^2.8.5",
     "dotenv": "^17.2.1",
     "express": "^4.18.2",
+    "express-rate-limit": "^7.4.0",
     "groq-sdk": "^0.30.0",
     "jsonwebtoken": "^9.0.2",
     "mongodb": "^6.20.0",