diff --git a/src/__tests__/email-change.test.ts b/src/__tests__/email-change.test.ts
new file mode 100644
index 0000000..d07ad5d
--- /dev/null
+++ b/src/__tests__/email-change.test.ts
@@ -0,0 +1,120 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import express from "express";
+import request from "supertest";
+
+vi.mock("../services/verification.js");
+vi.mock("../services/email.js");
+vi.mock("../services/db.js");
+vi.mock("../services/logger.js", () => ({
+  default: { info: vi.fn(), error: vi.fn(), warn: vi.fn(), debug: vi.fn() },
+}));
+
+let app: express.Express;
+
+beforeEach(async () => {
+  vi.clearAllMocks();
+  vi.resetModules();
+
+  const { createPendingVerification, verifyCode } = await import("../services/verification.js");
+  const { sendVerificationEmail } = await import("../services/email.js");
+  const { queryWithRetry } = await import("../services/db.js");
+
+  vi.mocked(createPendingVerification).mockResolvedValue({ email: "new@example.com", code: "123456", createdAt: "", expiresAt: "", attempts: 0 });
+  vi.mocked(verifyCode).mockResolvedValue({ status: "ok" });
+  vi.mocked(sendVerificationEmail).mockResolvedValue(true);
+  // Default: apiKey exists, email not taken
+  vi.mocked(queryWithRetry).mockImplementation(async (sql: string, params?: any[]) => {
+    if (sql.includes("SELECT") && sql.includes("api_keys") && sql.includes("key =")) {
+      return { rows: [{ key: "df_pro_xxx", email: "old@example.com", tier: "pro" }], rowCount: 1 };
+    }
+    if (sql.includes("SELECT") && sql.includes("api_keys") && sql.includes("email =")) {
+      return { rows: [], rowCount: 0 };
+    }
+    if (sql.includes("UPDATE")) {
+      return { rows: [{ email: "new@example.com" }], rowCount: 1 };
+    }
+    return { rows: [], rowCount: 0 };
+  });
+
+  const { emailChangeRouter } = await import("../routes/email-change.js");
+  app = express();
+  app.use(express.json());
+  app.use("/v1/email-change", emailChangeRouter);
+});
+
+describe("POST /v1/email-change", () => {
+  it("returns 400 for missing apiKey", async () => {
+    const res = await request(app).post("/v1/email-change").send({ newEmail: "new@example.com" });
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 400 for missing newEmail", async () => {
+    const res = await request(app).post("/v1/email-change").send({ apiKey: "df_pro_xxx" });
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 400 for invalid email format", async () => {
+    const res = await request(app).post("/v1/email-change").send({ apiKey: "df_pro_xxx", newEmail: "bad" });
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 403 for invalid API key", async () => {
+    const { queryWithRetry } = await import("../services/db.js");
+    vi.mocked(queryWithRetry).mockImplementation(async (sql: string) => {
+      if (sql.includes("SELECT") && sql.includes("key =")) {
+        return { rows: [], rowCount: 0 };
+      }
+      return { rows: [], rowCount: 0 };
+    });
+    const res = await request(app).post("/v1/email-change").send({ apiKey: "fake", newEmail: "new@example.com" });
+    expect(res.status).toBe(403);
+  });
+
+  it("returns 409 when email already taken", async () => {
+    const { queryWithRetry } = await import("../services/db.js");
+    vi.mocked(queryWithRetry).mockImplementation(async (sql: string) => {
+      if (sql.includes("SELECT") && sql.includes("key =")) {
+        return { rows: [{ key: "df_pro_xxx", email: "old@example.com" }], rowCount: 1 };
+      }
+      if (sql.includes("SELECT") && sql.includes("email =")) {
+        return { rows: [{ key: "df_pro_other", email: "new@example.com" }], rowCount: 1 };
+      }
+      return { rows: [], rowCount: 0 };
+    });
+    const res = await request(app).post("/v1/email-change").send({ apiKey: "df_pro_xxx", newEmail: "new@example.com" });
+    expect(res.status).toBe(409);
+  });
+
+  it("returns 200 with verification_sent on success", async () => {
+    const res = await request(app).post("/v1/email-change").send({ apiKey: "df_pro_xxx", newEmail: "new@example.com" });
+    expect(res.status).toBe(200);
+    expect(res.body.status).toBe("verification_sent");
+  });
+});
+
+describe("POST /v1/email-change/verify", () => {
+  it("returns 400 for missing fields", async () => {
+    const res = await request(app).post("/v1/email-change/verify").send({ apiKey: "df_pro_xxx" });
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 400 for invalid code", async () => {
+    const { verifyCode } = await import("../services/verification.js");
+    vi.mocked(verifyCode).mockResolvedValue({ status: "invalid" });
+    const res = await request(app).post("/v1/email-change/verify").send({ apiKey: "df_pro_xxx", newEmail: "new@example.com", code: "999999" });
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 200 and updates email on success", async () => {
+    const { queryWithRetry } = await import("../services/db.js");
+    const res = await request(app).post("/v1/email-change/verify").send({ apiKey: "df_pro_xxx", newEmail: "new@example.com", code: "123456" });
+    expect(res.status).toBe(200);
+    expect(res.body.status).toBe("ok");
+    expect(res.body.newEmail).toBe("new@example.com");
+    // Verify UPDATE was called
+    expect(queryWithRetry).toHaveBeenCalledWith(
+      expect.stringContaining("UPDATE"),
+      expect.arrayContaining(["new@example.com", "df_pro_xxx"])
+    );
+  });
+});
diff --git a/src/index.ts b/src/index.ts
index a0499b3..7ba5b7e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -15,6 +15,7 @@ import { templatesRouter } from "./routes/templates.js";
 import { healthRouter } from "./routes/health.js";
 import { demoRouter } from "./routes/demo.js";
 import { recoverRouter } from "./routes/recover.js";
+import { emailChangeRouter } from "./routes/email-change.js";
 import { billingRouter } from "./routes/billing.js";
 import { authMiddleware } from "./middleware/auth.js";
 import { usageMiddleware, loadUsageData } from "./middleware/usage.js";
@@ -130,6 +131,7 @@ app.use("/v1/signup", (_req, res) => {
   });
 });
 app.use("/v1/recover", recoverRouter);
+app.use("/v1/email-change", emailChangeRouter);
 app.use("/v1/billing", billingRouter);
 
 // Authenticated routes — conversion routes get tighter body limits (500KB)
diff --git a/src/routes/email-change.ts b/src/routes/email-change.ts
new file mode 100644
index 0000000..3041b15
--- /dev/null
+++ b/src/routes/email-change.ts
@@ -0,0 +1,204 @@
+import { Router, Request, Response } from "express";
+import rateLimit from "express-rate-limit";
+import { createPendingVerification, verifyCode } from "../services/verification.js";
+import { sendVerificationEmail } from "../services/email.js";
+import { queryWithRetry } from "../services/db.js";
+import logger from "../services/logger.js";
+
+const router = Router();
+
+const emailChangeLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 3,
+  message: { error: "Too many email change attempts. Please try again in 1 hour." },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req: Request) => req.body?.apiKey || req.ip || "unknown",
+});
+
+const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+
+async function validateApiKey(apiKey: string) {
+  const result = await queryWithRetry(
+    `SELECT key, email, tier FROM api_keys WHERE key = $1`,
+    [apiKey]
+  );
+  return result.rows[0] || null;
+}
+
+/**
+ * @openapi
+ * /v1/email-change:
+ *   post:
+ *     tags: [Account]
+ *     summary: Request email change
+ *     description: |
+ *       Sends a 6-digit verification code to the new email address.
+ *       Rate limited to 3 requests per hour per API key.
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             required: [apiKey, newEmail]
+ *             properties:
+ *               apiKey:
+ *                 type: string
+ *               newEmail:
+ *                 type: string
+ *                 format: email
+ *     responses:
+ *       200:
+ *         description: Verification code sent
+ *         content:
+ *           application/json:
+ *             schema:
+ *               type: object
+ *               properties:
+ *                 status:
+ *                   type: string
+ *                   example: verification_sent
+ *                 message:
+ *                   type: string
+ *       400:
+ *         description: Missing or invalid fields
+ *       403:
+ *         description: Invalid API key
+ *       409:
+ *         description: Email already taken
+ *       429:
+ *         description: Too many attempts
+ */
+router.post("/", emailChangeLimiter, async (req: Request, res: Response) => {
+  const { apiKey, newEmail } = req.body || {};
+
+  if (!apiKey || typeof apiKey !== "string") {
+    res.status(400).json({ error: "apiKey is required." });
+    return;
+  }
+
+  if (!newEmail || typeof newEmail !== "string") {
+    res.status(400).json({ error: "newEmail is required." });
+    return;
+  }
+
+  const cleanEmail = newEmail.trim().toLowerCase();
+
+  if (!EMAIL_RE.test(cleanEmail)) {
+    res.status(400).json({ error: "Invalid email format." });
+    return;
+  }
+
+  const keyRow = await validateApiKey(apiKey);
+  if (!keyRow) {
+    res.status(403).json({ error: "Invalid API key." });
+    return;
+  }
+
+  // Check if email is already taken by another key
+  const existing = await queryWithRetry(
+    `SELECT key FROM api_keys WHERE email = $1 AND key != $2`,
+    [cleanEmail, apiKey]
+  );
+  if (existing.rows.length > 0) {
+    res.status(409).json({ error: "This email is already associated with another account." });
+    return;
+  }
+
+  const pending = await createPendingVerification(cleanEmail);
+
+  sendVerificationEmail(cleanEmail, pending.code).catch(err => {
+    logger.error({ err, email: cleanEmail }, "Failed to send email change verification");
+  });
+
+  res.json({ status: "verification_sent", message: "A verification code has been sent to your new email address." });
+});
+
+/**
+ * @openapi
+ * /v1/email-change/verify:
+ *   post:
+ *     tags: [Account]
+ *     summary: Verify email change code
+ *     description: Verifies the 6-digit code and updates the account email.
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             required: [apiKey, newEmail, code]
+ *             properties:
+ *               apiKey:
+ *                 type: string
+ *               newEmail:
+ *                 type: string
+ *                 format: email
+ *               code:
+ *                 type: string
+ *                 pattern: '^\d{6}$'
+ *     responses:
+ *       200:
+ *         description: Email updated
+ *         content:
+ *           application/json:
+ *             schema:
+ *               type: object
+ *               properties:
+ *                 status:
+ *                   type: string
+ *                   example: ok
+ *                 newEmail:
+ *                   type: string
+ *       400:
+ *         description: Missing fields or invalid code
+ *       403:
+ *         description: Invalid API key
+ *       410:
+ *         description: Code expired
+ *       429:
+ *         description: Too many failed attempts
+ */
+router.post("/verify", async (req: Request, res: Response) => {
+  const { apiKey, newEmail, code } = req.body || {};
+
+  if (!apiKey || !newEmail || !code) {
+    res.status(400).json({ error: "apiKey, newEmail, and code are required." });
+    return;
+  }
+
+  const cleanEmail = newEmail.trim().toLowerCase();
+  const cleanCode = String(code).trim();
+
+  const keyRow = await validateApiKey(apiKey);
+  if (!keyRow) {
+    res.status(403).json({ error: "Invalid API key." });
+    return;
+  }
+
+  const result = await verifyCode(cleanEmail, cleanCode);
+
+  switch (result.status) {
+    case "ok": {
+      await queryWithRetry(
+        `UPDATE api_keys SET email = $1 WHERE key = $2`,
+        [cleanEmail, apiKey]
+      );
+      logger.info({ apiKey: apiKey.slice(0, 10) + "...", newEmail: cleanEmail }, "Email changed");
+      res.json({ status: "ok", newEmail: cleanEmail });
+      break;
+    }
+    case "expired":
+      res.status(410).json({ error: "Verification code has expired. Please request a new one." });
+      break;
+    case "max_attempts":
+      res.status(429).json({ error: "Too many failed attempts. Please request a new code." });
+      break;
+    case "invalid":
+      res.status(400).json({ error: "Invalid verification code." });
+      break;
+  }
+});
+
+export { router as emailChangeRouter };