What is the name of Microsoft's hypervisor?

Microsoft's hypervisor is called Hyper-V.

Hyper-V is Microsoft's hardware virtualization platform for creating and running virtual machines. It is built into selected editions of Windows and Windows Server, and it allows one physical computer to host multiple isolated operating systems. Each virtual machine can have its own virtual processor, memory, storage, and network interfaces.

Microsoft introduced the technology under the code name Viridian, and it was also called Windows Server Virtualization during development. Hyper-V first became available as a production role in Windows Server 2008. On client versions of Windows, it is offered in editions such as Windows 10 and Windows 11 Pro, Enterprise, and Education, subject to hardware and firmware requirements.

The alternatives are different virtualization products: Xen is an open-source hypervisor, KVM is integrated into the Linux kernel, and VMware ESXi is VMware's bare-metal hypervisor. Hyper-V is Microsoft's counterpart in that group, not a general name for virtualization itself.