Abstract: Systems and methods for single sign on to a cloud. The system includes a cloud service provider and a tenant. The cloud service provider has a consumer unit and a portal. The consumer unit provides an interface for a user to connect to the cloud service provider. The portal providing a cloud service to the user, the portal has a first authentication system that issues a security token request and that is connected to the consumer unit. The tenant includes the user and a second authentication system. The second authentication system signs the security token request. The consumer unit is adapted to communicate with the first authentication system using a first protocol and adapted to communicate with the second authentication system using a second protocol.