The HTTP status code that indicates a successful request is 200 OK. This response code is returned by web servers to indicate that a request from a client was successfully processed. It signifies that the requested resource (like a webpage or API endpoint) is available and that the server has returned the data that was requested. Status codes in the 200 range typically indicate that the client's request was understood and accepted by the server without issues. Understanding these codes is crucial for developers and users to troubleshoot and diagnose issues related to web communications effectively.