In this paper, the authors present a review on the various methods of authentication in cloud environment. Authentication plays an important role in security of Cloud Computing (CC). It protects Cloud Service Providers (CSP) against various types of attacks, where the aim is to verify a user's identity when a user wishes to request services from cloud servers. There are multiple authentication technologies that verify the identity of a user before granting access to resources. Cloud computing is a model for enabling on demand network access to a shared data, infrastructure, software and platform resources which can be rapidly provisioned and released with minimal management effort or service provider interaction.