**Requirements:** a MailChimp account (section 2). 1. Click your profile icon and choose **Account**. 2. Open the **Extras** dropdown and select **API keys**. 3. In the "Your API Keys" section, click **Create A Key**. 4. Give it a recognizable name — for example the app that will use it, never a generic one like "test". 5. Click **Generate Key** and then **Copy Key to Clipboard** — MailChimp only shows the full key immediately after generating it; from then on, your key list will only show its name and its first four digits. > **Note — The datacenter is embedded in the key itself** > > Unlike other integrations, there's no need to state the datacenter separately: it's encoded in the key's own suffix (for example, the `-us6` at the end) — the Platform detects it automatically when connecting. > **Notice — Transactional emails: a separate, optional key** > > If you also want the "Event → transactional email" action (section 5) to work, you need a **Mandrill API key** (Mailchimp Transactional) — a product and billing DIFFERENT from your Marketing account, with its own sign-up. Without that key, the integration syncs contacts and tags normally; that specific action just doesn't get to send anything. Verified against MailChimp's official documentation (`mailchimp.com/help/about-api-keys/`, checked on September 5, 2026).