Windows Phone 7 (WP7) is the first release of the Windows Phone mobile client operating system, released worldwide on October 21, 2010, and in the United States on November 8, 2010. It runs on the Windows CE 6.0 R3 kernel. It serves as the successor to Windows Mobile 6.5.

Windows Phone 7 was a complete overhaul of Microsoft's previous mobile Windows platforms. It was designed