Windows Mobile was a family of mobile operating systems developed by Microsoft for smartphones and personal digital assistants.

Its origin dated back to Windows CE in 1996, though Windows Mobile itself first appeared in 2000 as Pocket PC 2000 which ran on Pocket PC PDAs. It was renamed "Windows Mobile" in 2003, at which point it came in several versions (similar to the desktop versions of Windows) and was aimed at business and enterprise consumers. When initially released in the mid-2000s, it was to be the portable equivalent of what Windows desktop OS was: a major force in the then-emerging mobile/portable areas.

Following the rise of newer smartphone OSs (iOS and Android) Windows Mobile never equalled the success and faded rapidly in the following years. By February 2010, Microsoft announced the more modern and consumer-focused Windows Phone to supersede Windows Mobile. As a result, Windows Mobile has been deprecated since existing devices and software are incompatible with Windows Phone. The last version of Windows Mobile, released after the announcement of Windows Phone, was 6.5.5. After this, Microsoft ceased development on Windows Mobile in order to concentrate on Windows Phone.

Microsoft released a similarly-named Windows 10 Mobile in 2015 which was part of the Windows Phone series, and it is unrelated to the former Windows Mobile operating systems.