HTTP Status Code 401 means Unauthorized. This code indicates that the client must authenticate itself to get the requested response. Essentially, the request was received by the server, but the client failed to provide valid authentication credentials. The server response will often include a WWW-Authenticate header with information about how to authenticate. A 401 error is distinct from a 403 Forbidden error, as 401 specifically relates to missing or invalid authentication rather than general access permissions.