diff --git a/src/createMollieClient.ts b/src/createMollieClient.ts
index 5a2d1968..60be6828 100644
--- a/src/createMollieClient.ts
+++ b/src/createMollieClient.ts
@@ -31,25 +31,29 @@ import RefundsResource from './resources/refunds/RefundsResource';
 import SubscriptionsResource from './resources/subscriptions/SubscriptionsResource';
 import SubscriptionsPaymentsResource from './resources/subscriptions/payments/SubscriptionsPaymentsResource';
 
-export type MollieOptions = AxiosRequestConfig & {
+export type MollieOptions = Xor<
+  {
+    /**
+     * The Mollie API key, starting with `'test_'` or `'live_'`.
+     */
+    apiKey: string;
+  },
+  {
+    /**
+     * OAuth access token, starting with `'access_''.
+     */
+    accessToken: string;
+  }
+> & {
   /**
    * One or an array of version strings of the software you are using, such as `'RockenbergCommerce/3.1.12'`.
    */
   versionStrings?: string | string[];
-} & Xor<
-    {
-      /**
-       * The Mollie API key, starting with `'test_'` or `'live_'`.
-       */
-      apiKey: string;
-    },
-    {
-      /**
-       * OAuth access token, starting with `'access_''.
-       */
-      accessToken: string;
-    }
-  >;
+  /**
+   * The URL of the root of the Mollie API. Default: `'https://api.mollie.com:443/v2/'`.
+   */
+  apiEndpoint?: string;
+} & Pick<AxiosRequestConfig, 'adapter' | 'headers' | 'proxy' | 'socketPath' | 'timeout'>;
 
 function preprocessVersionStrings(input: string | string[] | undefined): string[] {
   if (Array.isArray(input)) {
@@ -60,14 +64,10 @@ function preprocessVersionStrings(input: string | string[] | undefined): string[
   }
   return [];
 }
-function createHttpClient({ apiKey, accessToken, versionStrings, ...axiosOptions }: MollieOptions): AxiosInstance {
-  axiosOptions.baseURL = 'https://api.mollie.com:443/v2/';
-
-  if (axiosOptions.headers == undefined) {
-    axiosOptions.headers = {};
-  }
+function createHttpClient({ apiKey, accessToken, versionStrings, apiEndpoint = 'https://api.mollie.com:443/v2/', ...axiosOptions }: MollieOptions): AxiosInstance {
+  const headers: Record<string, string> = axiosOptions.headers ?? {};
 
-  axiosOptions.headers['User-Agent'] = [
+  headers['User-Agent'] = [
     `Node/${process.version}`,
     `Mollie/${libraryVersion}`,
     ...preprocessVersionStrings(versionStrings).map(versionString => {
@@ -91,19 +91,22 @@ function createHttpClient({ apiKey, accessToken, versionStrings, ...axiosOptions
   ].join(' ');
 
   if (apiKey != undefined) {
-    axiosOptions.headers['Authorization'] = `Bearer ${apiKey}`;
+    headers['Authorization'] = `Bearer ${apiKey}`;
   } /* if (accessToken != undefined) */ else {
-    axiosOptions.headers['Authorization'] = `Bearer ${accessToken}`;
-    axiosOptions.headers['User-Agent'] += ' OAuth/2.0';
+    headers['Authorization'] = `Bearer ${accessToken}`;
+    headers['User-Agent'] += ' OAuth/2.0';
   }
-  axiosOptions.headers['Accept-Encoding'] = 'gzip';
-  axiosOptions.headers['Content-Type'] = 'application/json';
-
-  axiosOptions.httpsAgent = new https.Agent({
-    ca: caCertificates,
+  headers['Accept-Encoding'] = 'gzip';
+  headers['Content-Type'] = 'application/json';
+
+  return axios.create({
+    ...axiosOptions,
+    baseURL: apiEndpoint,
+    headers,
+    httpsAgent: new https.Agent({
+      ca: caCertificates,
+    }),
   });
-
-  return axios.create(axiosOptions);
 }
 
 /**
@@ -112,7 +115,7 @@ function createHttpClient({ apiKey, accessToken, versionStrings, ...axiosOptions
  */
 export default function createMollieClient(options: MollieOptions) {
   // Attempt to catch cases where this library is integrated into a frontend app.
-  if (['node', 'io.js'].indexOf(process?.release?.name) == -1) {
+  if (['node', 'io.js'].includes(process?.release?.name) == false) {
     throw new Error(
       `Unexpected process release name ${process?.release?.name}. This may indicate that the Mollie API client is integrated into a website or app. This is not recommended, please see https://github.com/mollie/mollie-api-node/#a-note-on-use-outside-of-nodejs. If this is a mistake, please let us know: https://github.com/mollie/mollie-api-node/issues`,
     );
diff --git a/tests/unit/networking.test.ts b/tests/unit/networking.test.ts
index cfa8d81a..f2c8185c 100644
--- a/tests/unit/networking.test.ts
+++ b/tests/unit/networking.test.ts
@@ -40,7 +40,7 @@ test('defaults', async () => {
 });
 
 async function requestWithVersionStrings(versionStrings: string | string[] | undefined) {
-  const { adapter, client } = wireMockClient(versionStrings);
+  const { adapter, client } = wireMockClient({ versionStrings });
 
   adapter.onGet('/customers').reply(200, {
     _embedded: {
@@ -91,3 +91,30 @@ test('customVersionStrings', async () => {
 
   expect(headers['User-Agent'].endsWith('phpCookbookForNodeUsers/7.3.4')).toBe(true);
 });
+
+test('customApiEndpoint', async () => {
+  const { adapter, client } = wireMockClient({ apiEndpoint: 'https://null.house/' });
+
+  adapter.onGet('/customers').reply(200, {
+    _embedded: {
+      customers: [],
+    },
+    count: 0,
+    _links: {
+      documentation: {
+        href: 'https://docs.mollie.com/reference/v2/customers-api/list-customers',
+        type: 'text/html',
+      },
+      self: {
+        href: 'https://api.mollie.com/v2/customers?limit=50',
+        type: 'application/hal+json',
+      },
+      previous: null,
+      next: null,
+    },
+  });
+
+  await bluster(client.customers.all.bind(client.customers))();
+
+  expect(adapter.history.get[0].baseURL).toBe('https://null.house/');
+});
diff --git a/tests/wireMockClient.ts b/tests/wireMockClient.ts
index aa09a48f..43ff74e9 100644
--- a/tests/wireMockClient.ts
+++ b/tests/wireMockClient.ts
@@ -1,16 +1,16 @@
-import createMollieClient, { MollieClient } from '..';
+import createMollieClient, { MollieClient, MollieOptions } from '..';
 import { AxiosInstance } from 'axios';
 import MockAdapter from 'axios-mock-adapter';
 import {} from 'jest-bluster';
 
-export default function wireMockClient(versionStrings?: string | string[]): { adapter: MockAdapter; client: MollieClient } {
+export default function wireMockClient(options?: Omit<MollieOptions, 'accessToken' | 'adapter' | 'apiKey'>): { adapter: MockAdapter; client: MollieClient } {
   const adapter = new MockAdapter((undefined as unknown) as AxiosInstance);
   return {
     adapter,
     client: createMollieClient({
       apiKey: 'mock-api-key',
       adapter: adapter.adapter(),
-      versionStrings,
+      ...options,
     }),
   };
 }