HTTP Status Code 407 indicates Proxy Authentication Required. This status is sent when a client must authenticate itself with a proxy server before the request can proceed. It implies that the requested resource is accessible only after the client has provided valid credentials to the proxy. The server response will include a Proxy-Authenticate header field containing the authentication method required to gain access through the proxy. Essentially, it informs the client that it needs to authenticate with the proxy server to continue with the original request.