diff --git a/packages/@emulators/polar/package.json b/packages/@emulators/polar/package.json
new file mode 100644
index 00000000..99922035
--- /dev/null
+++ b/packages/@emulators/polar/package.json
@@ -0,0 +1,45 @@
+{
+  "name": "@emulators/polar",
+  "version": "0.6.1",
+  "license": "Apache-2.0",
+  "type": "module",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js",
+      "types": "./dist/index.d.ts"
+    }
+  },
+  "homepage": "https://emulate.dev",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/vercel-labs/emulate.git",
+    "directory": "packages/@emulators/polar"
+  },
+  "bugs": {
+    "url": "https://github.com/vercel-labs/emulate/issues"
+  },
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsup --clean",
+    "dev": "tsup --watch",
+    "test": "vitest run",
+    "clean": "rm -rf dist .turbo",
+    "type-check": "tsc --noEmit",
+    "lint": "eslint src"
+  },
+  "dependencies": {
+    "@emulators/core": "workspace:*"
+  },
+  "devDependencies": {
+    "tsup": "^8",
+    "typescript": "^5.7",
+    "vitest": "^4.1.0"
+  }
+}
\ No newline at end of file
diff --git a/packages/@emulators/polar/src/__tests__/polar.test.ts b/packages/@emulators/polar/src/__tests__/polar.test.ts
new file mode 100644
index 00000000..7256e817
--- /dev/null
+++ b/packages/@emulators/polar/src/__tests__/polar.test.ts
@@ -0,0 +1,97 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { Hono } from "@emulators/core";
+import {
+  Store,
+  WebhookDispatcher,
+  authMiddleware,
+  createApiErrorHandler,
+  createErrorHandler,
+  type TokenMap,
+} from "@emulators/core";
+import { polarPlugin, seedFromConfig, getPolarStore } from "../index.js";
+
+const base = "http://localhost:4000";
+
+function createTestApp() {
+  const store = new Store();
+  const webhooks = new WebhookDispatcher();
+  const tokenMap: TokenMap = new Map();
+  tokenMap.set("polar_test_token", {
+    login: "testuser@example.com",
+    id: 1,
+    scopes: [],
+  });
+
+  const app = new Hono();
+  app.onError(createApiErrorHandler());
+  app.use("*", createErrorHandler());
+  app.use("*", authMiddleware(tokenMap));
+  polarPlugin.register(app as any, store, webhooks, base, tokenMap);
+
+  return { app, store, webhooks, tokenMap };
+}
+
+function authHeaders(): Record<string, string> {
+  return { Authorization: "Bearer polar_test_token", "Content-Type": "application/json" };
+}
+
+describe("Polar plugin", () => {
+  let app: Hono;
+  let store: Store;
+
+  beforeEach(() => {
+    const testApp = createTestApp();
+    app = testApp.app;
+    store = testApp.store;
+  });
+
+  it("seeds and lists organizations and products", async () => {
+    seedFromConfig(store, base, {
+      organizations: [{ name: "My Org", slug: "my-org" }],
+      products: [{ name: "Pro Plan", price: 2000, organization_slug: "my-org" }],
+    });
+
+    const resOrgs = await app.request(`${base}/v1/organizations`, { headers: authHeaders() });
+    expect(resOrgs.status).toBe(200);
+    const orgsBody = (await resOrgs.json()) as any;
+    expect(orgsBody.items.length).toBe(1);
+    expect(orgsBody.items[0].slug).toBe("my-org");
+
+    const resProds = await app.request(`${base}/v1/products`, { headers: authHeaders() });
+    expect(resProds.status).toBe(200);
+    const prodsBody = (await resProds.json()) as any;
+    expect(prodsBody.items.length).toBe(1);
+    expect(prodsBody.items[0].name).toBe("Pro Plan");
+    expect(prodsBody.items[0].price).toBe(2000);
+  });
+
+  it("creates and retrieves custom checkout", async () => {
+    const ps = getPolarStore(store);
+    
+    // Seed a product first
+    const prod = ps.products.insert({
+      polar_id: "prod_123",
+      name: "Standard Plan",
+      price: 1000,
+      organization_id: "org_123",
+    });
+
+    const resCreate = await app.request(`${base}/v1/checkouts/custom`, {
+      method: "POST",
+      headers: authHeaders(),
+      body: JSON.stringify({
+        product_id: "prod_123",
+        customer_email: "user@example.com",
+      }),
+    });
+    expect(resCreate.status).toBe(201);
+    const created = (await resCreate.json()) as any;
+    expect(created.id).toBeDefined();
+    expect(created.product_id).toBe("prod_123");
+
+    const resGet = await app.request(`${base}/v1/checkouts/custom/${created.id}`, { headers: authHeaders() });
+    expect(resGet.status).toBe(200);
+    const retrieved = (await resGet.json()) as any;
+    expect(retrieved.id).toBe(created.id);
+  });
+});
diff --git a/packages/@emulators/polar/src/entities.ts b/packages/@emulators/polar/src/entities.ts
new file mode 100644
index 00000000..bdf138d9
--- /dev/null
+++ b/packages/@emulators/polar/src/entities.ts
@@ -0,0 +1,32 @@
+import type { Entity } from "@emulators/core";
+
+export interface PolarOrganization extends Entity {
+  polar_id: string;
+  name: string;
+  slug: string;
+}
+
+export interface PolarProduct extends Entity {
+  polar_id: string;
+  name: string;
+  description?: string;
+  price: number;
+  organization_id: string;
+}
+
+export interface PolarCheckout extends Entity {
+  polar_id: string;
+  url: string;
+  status: "open" | "confirmed" | "failed";
+  product_id: string;
+  organization_id: string;
+  customer_email?: string;
+}
+
+export interface PolarSubscription extends Entity {
+  polar_id: string;
+  status: "active" | "canceled";
+  user_id: string;
+  product_id: string;
+  organization_id: string;
+}
diff --git a/packages/@emulators/polar/src/formatters.ts b/packages/@emulators/polar/src/formatters.ts
new file mode 100644
index 00000000..1ba408a1
--- /dev/null
+++ b/packages/@emulators/polar/src/formatters.ts
@@ -0,0 +1,41 @@
+import type { PolarOrganization, PolarProduct, PolarCheckout, PolarSubscription } from "../entities.js";
+
+export function formatOrganization(o: PolarOrganization) {
+  return {
+    id: o.polar_id,
+    name: o.name,
+    slug: o.slug,
+  };
+}
+
+export function formatProduct(p: PolarProduct) {
+  return {
+    id: p.polar_id,
+    name: p.name,
+    description: p.description,
+    price: p.price,
+    organization_id: p.organization_id,
+  };
+}
+
+export function formatCheckout(c: PolarCheckout) {
+  return {
+    id: c.polar_id,
+    client_secret: "mock_client_secret_" + c.polar_id,
+    url: c.url,
+    status: c.status,
+    product_id: c.product_id,
+    organization_id: c.organization_id,
+    customer_email: c.customer_email,
+  };
+}
+
+export function formatSubscription(s: PolarSubscription) {
+  return {
+    id: s.polar_id,
+    status: s.status,
+    user_id: s.user_id,
+    product_id: s.product_id,
+    organization_id: s.organization_id,
+  };
+}
diff --git a/packages/@emulators/polar/src/helpers.ts b/packages/@emulators/polar/src/helpers.ts
new file mode 100644
index 00000000..cec0516d
--- /dev/null
+++ b/packages/@emulators/polar/src/helpers.ts
@@ -0,0 +1,5 @@
+import { randomUUID } from "crypto";
+
+export function generateUuid(): string {
+  return randomUUID();
+}
diff --git a/packages/@emulators/polar/src/index.ts b/packages/@emulators/polar/src/index.ts
new file mode 100644
index 00000000..71d0eadb
--- /dev/null
+++ b/packages/@emulators/polar/src/index.ts
@@ -0,0 +1,74 @@
+import type { Hono } from "@emulators/core";
+import type { ServicePlugin, Store, WebhookDispatcher, TokenMap, AppEnv, RouteContext } from "@emulators/core";
+import { getPolarStore } from "./store.js";
+import { generateUuid } from "./helpers.js";
+import { organizationRoutes } from "./routes/organizations.js";
+import { productRoutes } from "./routes/products.js";
+import { checkoutRoutes } from "./routes/checkouts.js";
+import { subscriptionRoutes } from "./routes/subscriptions.js";
+
+export { getPolarStore, type PolarStore } from "./store.js";
+export * from "./entities.js";
+
+export interface PolarSeedConfig {
+  organizations?: Array<{
+    name: string;
+    slug: string;
+  }>;
+  products?: Array<{
+    name: string;
+    description?: string;
+    price: number;
+    organization_slug?: string;
+  }>;
+}
+
+export function seedFromConfig(store: Store, _baseUrl: string, config: PolarSeedConfig): void {
+  const ps = getPolarStore(store);
+
+  if (config.organizations) {
+    for (const o of config.organizations) {
+      if (ps.organizations.findOneBy("slug", o.slug)) continue;
+      ps.organizations.insert({
+        polar_id: generateUuid(),
+        name: o.name,
+        slug: o.slug,
+      });
+    }
+  }
+
+  if (config.products) {
+    for (const p of config.products) {
+      let orgId = "default_org";
+      if (p.organization_slug) {
+        const org = ps.organizations.findOneBy("slug", p.organization_slug);
+        if (org) {
+          orgId = org.polar_id;
+        }
+      }
+      ps.products.insert({
+        polar_id: generateUuid(),
+        name: p.name,
+        description: p.description,
+        price: p.price,
+        organization_id: orgId,
+      });
+    }
+  }
+}
+
+export const polarPlugin: ServicePlugin = {
+  name: "polar",
+  register(app: Hono<AppEnv>, store: Store, webhooks: WebhookDispatcher, baseUrl: string, tokenMap?: TokenMap): void {
+    const ctx: RouteContext = { app, store, webhooks, baseUrl, tokenMap };
+    organizationRoutes(ctx);
+    productRoutes(ctx);
+    checkoutRoutes(ctx);
+    subscriptionRoutes(ctx);
+  },
+  seed(_store: Store, _baseUrl: string): void {
+    // Empty default seed
+  },
+};
+
+export default polarPlugin;
diff --git a/packages/@emulators/polar/src/routes/checkouts.ts b/packages/@emulators/polar/src/routes/checkouts.ts
new file mode 100644
index 00000000..f91231b6
--- /dev/null
+++ b/packages/@emulators/polar/src/routes/checkouts.ts
@@ -0,0 +1,56 @@
+import type { RouteContext } from "@emulators/core";
+import { getPolarStore } from "../store.js";
+import { generateUuid } from "../helpers.js";
+import { formatCheckout } from "../formatters.js";
+
+export function checkoutRoutes({ app, store, webhooks }: RouteContext): void {
+  const ps = getPolarStore(store);
+
+  app.post("/v1/checkouts/custom", async (c) => {
+    let body: any = {};
+    try {
+      body = await c.req.json();
+    } catch {
+      // Empty
+    }
+
+    const productId = body.product_id;
+    if (!productId) {
+      return c.json({ error: "Missing product_id" }, 400);
+    }
+
+    const prod = ps.products.findOneBy("polar_id", productId);
+    const orgId = prod ? prod.organization_id : "default_org";
+
+    const checkoutId = generateUuid();
+    const checkout = ps.checkouts.insert({
+      polar_id: checkoutId,
+      url: `https://polar.sh/checkout/${checkoutId}`,
+      status: "open",
+      product_id: productId,
+      organization_id: orgId,
+      customer_email: body.customer_email || undefined,
+    });
+
+    await webhooks.dispatch(
+      "checkout.created",
+      undefined,
+      {
+        type: "checkout.created",
+        data: formatCheckout(checkout),
+      },
+      "polar"
+    );
+
+    return c.json(formatCheckout(checkout), 201);
+  });
+
+  app.get("/v1/checkouts/custom/:id", (c) => {
+    const id = c.req.param("id");
+    const checkout = ps.checkouts.findOneBy("polar_id", id);
+    if (!checkout) {
+      return c.json({ error: "Checkout not found" }, 404);
+    }
+    return c.json(formatCheckout(checkout), 200);
+  });
+}
diff --git a/packages/@emulators/polar/src/routes/organizations.ts b/packages/@emulators/polar/src/routes/organizations.ts
new file mode 100644
index 00000000..3ca20899
--- /dev/null
+++ b/packages/@emulators/polar/src/routes/organizations.ts
@@ -0,0 +1,18 @@
+import type { RouteContext } from "@emulators/core";
+import { getPolarStore } from "../store.js";
+import { formatOrganization } from "../formatters.js";
+
+export function organizationRoutes({ app, store }: RouteContext): void {
+  const ps = getPolarStore(store);
+
+  app.get("/v1/organizations", (c) => {
+    const orgs = ps.organizations.all();
+    return c.json({
+      items: orgs.map(formatOrganization),
+      pagination: {
+        total_count: orgs.length,
+        max_page: 1,
+      }
+    }, 200);
+  });
+}
diff --git a/packages/@emulators/polar/src/routes/products.ts b/packages/@emulators/polar/src/routes/products.ts
new file mode 100644
index 00000000..db6bc305
--- /dev/null
+++ b/packages/@emulators/polar/src/routes/products.ts
@@ -0,0 +1,18 @@
+import type { RouteContext } from "@emulators/core";
+import { getPolarStore } from "../store.js";
+import { formatProduct } from "../formatters.js";
+
+export function productRoutes({ app, store }: RouteContext): void {
+  const ps = getPolarStore(store);
+
+  app.get("/v1/products", (c) => {
+    const prods = ps.products.all();
+    return c.json({
+      items: prods.map(formatProduct),
+      pagination: {
+        total_count: prods.length,
+        max_page: 1,
+      }
+    }, 200);
+  });
+}
diff --git a/packages/@emulators/polar/src/routes/subscriptions.ts b/packages/@emulators/polar/src/routes/subscriptions.ts
new file mode 100644
index 00000000..8141ae43
--- /dev/null
+++ b/packages/@emulators/polar/src/routes/subscriptions.ts
@@ -0,0 +1,18 @@
+import type { RouteContext } from "@emulators/core";
+import { getPolarStore } from "../store.js";
+import { formatSubscription } from "../formatters.js";
+
+export function subscriptionRoutes({ app, store }: RouteContext): void {
+  const ps = getPolarStore(store);
+
+  app.get("/v1/subscriptions", (c) => {
+    const subs = ps.subscriptions.all();
+    return c.json({
+      items: subs.map(formatSubscription),
+      pagination: {
+        total_count: subs.length,
+        max_page: 1,
+      }
+    }, 200);
+  });
+}
diff --git a/packages/@emulators/polar/src/store.ts b/packages/@emulators/polar/src/store.ts
new file mode 100644
index 00000000..6e36be9e
--- /dev/null
+++ b/packages/@emulators/polar/src/store.ts
@@ -0,0 +1,18 @@
+import { Store, type Collection } from "@emulators/core";
+import type { PolarOrganization, PolarProduct, PolarCheckout, PolarSubscription } from "./entities.js";
+
+export interface PolarStore {
+  organizations: Collection<PolarOrganization>;
+  products: Collection<PolarProduct>;
+  checkouts: Collection<PolarCheckout>;
+  subscriptions: Collection<PolarSubscription>;
+}
+
+export function getPolarStore(store: Store): PolarStore {
+  return {
+    organizations: store.collection<PolarOrganization>("polar.organizations", ["polar_id", "slug"]),
+    products: store.collection<PolarProduct>("polar.products", ["polar_id", "organization_id"]),
+    checkouts: store.collection<PolarCheckout>("polar.checkouts", ["polar_id", "product_id"]),
+    subscriptions: store.collection<PolarSubscription>("polar.subscriptions", ["polar_id", "user_id"]),
+  };
+}
diff --git a/packages/@emulators/polar/tsconfig.json b/packages/@emulators/polar/tsconfig.json
new file mode 100644
index 00000000..1b71a2df
--- /dev/null
+++ b/packages/@emulators/polar/tsconfig.json
@@ -0,0 +1,10 @@
+{
+  "extends": "../../../tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./dist",
+    "rootDir": "./src"
+  },
+  "include": [
+    "src/**/*"
+  ]
+}
\ No newline at end of file
diff --git a/packages/@emulators/polar/tsup.config.ts b/packages/@emulators/polar/tsup.config.ts
new file mode 100644
index 00000000..7a3d66a9
--- /dev/null
+++ b/packages/@emulators/polar/tsup.config.ts
@@ -0,0 +1,8 @@
+import { defineConfig } from "tsup";
+
+export default defineConfig({
+  entry: ["src/index.ts"],
+  format: ["esm"],
+  dts: true,
+  clean: true,
+});
diff --git a/packages/@emulators/polar/vitest.config.ts b/packages/@emulators/polar/vitest.config.ts
new file mode 100644
index 00000000..f624398e
--- /dev/null
+++ b/packages/@emulators/polar/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    environment: "node",
+  },
+});
diff --git a/packages/emulate/package.json b/packages/emulate/package.json
index b48ac8ed..5ae4ca0c 100644
--- a/packages/emulate/package.json
+++ b/packages/emulate/package.json
@@ -69,6 +69,7 @@
     "@emulators/vercel": "workspace:*",
     "@emulators/resend": "workspace:*",
     "@emulators/stripe": "workspace:*",
+    "@emulators/polar": "workspace:*",
     "@emulators/clerk": "workspace:*",
     "tsup": "^8",
     "typescript": "^5.7"
diff --git a/packages/emulate/src/registry.ts b/packages/emulate/src/registry.ts
index 41015811..04529ef4 100644
--- a/packages/emulate/src/registry.ts
+++ b/packages/emulate/src/registry.ts
@@ -25,6 +25,7 @@ const SERVICE_NAME_LIST = [
   "aws",
   "resend",
   "stripe",
+  "polar",
   "mongoatlas",
   "clerk",
 ] as const;
@@ -440,6 +441,23 @@ export const SERVICE_REGISTRY: Record<ServiceName, ServiceEntry> = {
       },
     },
   },
+  polar: {
+    label: "Polar.sh Merchant of Record emulator",
+    endpoints: "organizations, products, checkouts, subscriptions",
+    async load() {
+      const mod = await import("@emulators/polar");
+      return { plugin: mod.polarPlugin, seedFromConfig: mod.seedFromConfig };
+    },
+    defaultFallback() {
+      return { login: "admin", id: 1, scopes: [] };
+    },
+    initConfig: {
+      polar: {
+        organizations: [{ name: "My Org", slug: "my-org" }],
+        products: [{ name: "Pro Plan", price: 2000, organization_slug: "my-org" }],
+      },
+    },
+  },
   mongoatlas: {
     label: "MongoDB Atlas service emulator",
     endpoints:
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 3e4e036d..406f1514 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -613,6 +613,22 @@ importers:
         specifier: ^4.1.0
         version: 4.1.3(@opentelemetry/api@1.9.0)(@types/node@22.19.17)(vite@8.0.1(@emnapi/core@1.9.1)(@emnapi/runtime@1.9.1)(@types/node@22.19.17)(esbuild@0.27.4)(jiti@2.6.1)(yaml@2.8.3))
 
+  packages/@emulators/polar:
+    dependencies:
+      '@emulators/core':
+        specifier: workspace:*
+        version: link:../core
+    devDependencies:
+      tsup:
+        specifier: ^8
+        version: 8.5.1(jiti@2.6.1)(postcss@8.5.8)(typescript@5.9.3)(yaml@2.8.3)
+      typescript:
+        specifier: ^5.7
+        version: 5.9.3
+      vitest:
+        specifier: ^4.1.0
+        version: 4.1.3(@opentelemetry/api@1.9.0)(@types/node@22.19.17)(vite@8.0.1(@emnapi/core@1.9.1)(@emnapi/runtime@1.9.1)(@types/node@22.19.17)(esbuild@0.27.4)(jiti@2.6.1)(yaml@2.8.3))
+
   packages/@emulators/resend:
     dependencies:
       '@emulators/core':
@@ -722,6 +738,9 @@ importers:
       '@emulators/okta':
         specifier: workspace:*
         version: link:../@emulators/okta
+      '@emulators/polar':
+        specifier: workspace:*
+        version: link:../@emulators/polar
       '@emulators/resend':
         specifier: workspace:*
         version: link:../@emulators/resend