diff --git a/ENVIRONMENT.md b/ENVIRONMENT.md
index fa5af6a..2ce71ab 100644
--- a/ENVIRONMENT.md
+++ b/ENVIRONMENT.md
@@ -43,6 +43,7 @@ Admin requests are authenticated with a signed timestamp header. The timestamp *
 | `LOG_RETENTION_DAYS` | No | `90` | Age in days before notification logs and resolved indexer dead letters are pruned daily. Unresolved dead letters are retained. |
 | `NODE_ENV` | No | Unset (treated as development) | Set to `production` to switch logging to structured JSON instead of `pino-pretty`. Set automatically inside the Docker image. |
 | `HEALTH_CHECK_TIMEOUT_MS` | No | `3000` | Maximum duration in milliseconds allowed for each health-check dependency call before it is reported as degraded. |
+| `BODY_LIMIT_BYTES` | No | `1048576` | Maximum request body size in bytes (1 MiB). Must be a positive integer. Requests above the limit receive `413 { "error": "payload_too_large" }`. |
 | `RESEND_API_KEY` | No | — | Resend API key used to send NGO contact-email verification messages. Required, together with `NOTIFY_EMAIL_FROM` and `API_PUBLIC_URL`, for verification emails to be sent; other notification events remain in log-only stub mode. |
 | `NOTIFY_EMAIL_FROM` | No | — | Sender address used by Resend for contact-email verification. Required when `RESEND_API_KEY` is configured. |
 | `NOTIFY_EMAIL_TO` | No (planned) | — | Planned recipient address for notification emails. Not yet read by runtime code. |
diff --git a/src/server.ts b/src/server.ts
index f1ebfd6..9fc283e 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -87,9 +87,24 @@ export interface BuildServerOptions {
   trustProxy?: TrustProxySetting;
 }
 
+const DEFAULT_BODY_LIMIT_BYTES = 1_048_576;
+
+function configuredBodyLimit(): number {
+  const value = process.env.BODY_LIMIT_BYTES;
+  if (value === undefined || value.trim() === '') return DEFAULT_BODY_LIMIT_BYTES;
+  if (!/^\d+$/.test(value)) {
+    throw new Error('BODY_LIMIT_BYTES must be a positive integer.');
+  }
+  const parsed = Number(value);
+  if (!Number.isSafeInteger(parsed) || parsed < 1) {
+    throw new Error('BODY_LIMIT_BYTES must be a positive integer.');
+  }
+  return parsed;
+}
+
 export function buildServer(options?: BuildServerOptions) {
   const requestStartedAt = new WeakMap<object, bigint>();
-
+  const bodyLimit = configuredBodyLimit();
   const trustProxySetting =
     options?.trustProxy !== undefined
       ? options.trustProxy
@@ -97,6 +112,7 @@ export function buildServer(options?: BuildServerOptions) {
 
   const app = Fastify({
     ...requestIdOptions,
+    bodyLimit,
     logger: {
       level: process.env.LOG_LEVEL ?? 'info',
       transport: USE_PRETTY_LOGS
@@ -119,11 +135,16 @@ export function buildServer(options?: BuildServerOptions) {
     }
 
     const chunks: Buffer[] = [];
-
+    let receivedBytes = 0;
     for await (const chunk of payload) {
-      chunks.push(
-        Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string),
-      );
+      const bytes = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string);
+      receivedBytes += bytes.length;
+      if (receivedBytes > bodyLimit) {
+        const error = new Error('Request body is too large.') as FastifyError;
+        error.statusCode = 413;
+        throw error;
+      }
+      chunks.push(bytes);
     }
 
     const raw = Buffer.concat(chunks);
@@ -498,4 +519,4 @@ export function buildServer(options?: BuildServerOptions) {
   registerLogRetention(app);
 
   return app;
-}
\ No newline at end of file
+}
diff --git a/test/bodyLimit.test.ts b/test/bodyLimit.test.ts
new file mode 100644
index 0000000..c71e7c0
--- /dev/null
+++ b/test/bodyLimit.test.ts
@@ -0,0 +1,37 @@
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { buildServer } from '../src/server.js';
+
+describe('request body limit', () => {
+  const originalLimit = process.env.BODY_LIMIT_BYTES;
+
+  afterEach(() => {
+    if (originalLimit === undefined) delete process.env.BODY_LIMIT_BYTES;
+    else process.env.BODY_LIMIT_BYTES = originalLimit;
+  });
+
+  it('rejects oversized bodies using the standard 413 error response', async () => {
+    process.env.BODY_LIMIT_BYTES = '64';
+    const app = buildServer();
+    app.post('/test-body-limit', async (request) => request.body);
+
+    try {
+      const response = await app.inject({
+        method: 'POST',
+        url: '/test-body-limit',
+        headers: { 'content-type': 'application/json' },
+        payload: JSON.stringify({ value: 'x'.repeat(100) }),
+      });
+
+      expect(response.statusCode).toBe(413);
+      expect(response.json()).toEqual({ error: 'payload_too_large' });
+    } finally {
+      await app.close();
+    }
+  });
+
+  it('rejects invalid body-limit configuration', () => {
+    process.env.BODY_LIMIT_BYTES = 'not-a-number';
+    expect(() => buildServer()).toThrow('BODY_LIMIT_BYTES must be a positive integer.');
+  });
+});