Kerberos is a computer network authentication protocol, which allows individuals communicating over a non-secure network to prove their identity to one another in a secure manner. It is also a suite of free software published by Massachusetts Institute of Technology (MIT) that implements this protocol. Its designers aimed primarily at a client-server model, and it provides mutual authentication — both the user and the server verify each other's identity.

The Windows security model is based on the Kerberos security model.