All major:
- Microsoft Windows 10
- Microsoft Windows Server 2012 (Server 2016 not yet released by Microsoft at time of writing
- Ubuntu 14.14, 16.04
- SUSE Linux Enterprise Server 11 SP3, SLED 11SP3, SLES 12, SLED 12, SLED 12 SP1
- Scientific Linux 5.11, 6.6, 7.0, 7.1, 7.2
- Red Hat Enterprise Linux (RHEL) 5.10, 5.11, 6.5, 6.6, 7.0, 7.1, 7.2
- Oracle Enterprise Linux (OEL) 5.10, 5.11, 6.5, 6.6, 7.0, 7.1, 7.2
- Oracle UEK 6.5
- CentOS 5.10, 5.11, 6.5, 6.5, 7.0, 7.1
- Debian 7.2, 8.0

Refer to the XenServer 7.0 Virtual Machine User Guide for details: http://bit.ly/29xyuIQ