Microsoft Office for Mac 2011 currently supports Mac OS 10.5.8 and later. This includes 10.12 if fully patched (Office 2011 was last updated June 2017). All indications are however that this good luck streak may end with macOS 10.13 High Sierra.
Public beta testers of macOS 10.13 have reported that while Office 2011 apps will launch, they run at notably slower speeds, and experience frequent unexpected quits. Some have called it a “critically unstable experience”. For some, these problems appear to be limited to macOS 10.13 running on the new APFS file system, but others have reported similar issues with the HFS+ file system. Microsoft has posted that Office 2011 “Word, Excel, PowerPoint, Outlook and Lync have not been tested on macOS 10.13 High Sierra, and no formal support for this configuration will be provided.”
macOS 10.13 will be released this Fall, and coincidentally Microsoft is ending support for Office for Mac 2011 on 10/10/2017. No further Office 2011 updates will be released after that date.
If you’re still running Office 2011, and haven’t upgraded to Microsoft Office for Mac 2016 yet, play your cards wisely.