Citrix XenServer alternatives

Citrix XenServer
Citrix XenServer is an industry and value leading open-source virtualization platform for managing cloud, server and desktop virtual infrastructures. Organizations of any size can download XenServer for free to virtualize demanding workloads and automate management processes – increasing IT flexibility and agility and lowering costs.
Citrix XenServer alternatives are:
VMware vSphere, Microsoft Hyper-V, Citrix XenDesktop