Windows 8 is an upcoming version of Microsoft Windows, a series of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, Microsoft Tablet PCs, and Home theater PCs. According to unofficial sources, the release date for Windows 8 has been set for October 2012, three years after the release of its predecessor, Windows 7. Windows 8's server counterpart, Windows Server 2012, is in development concurrently with Windows 8. The most recent official pre-release version of Windows 8 is the Release Preview, which was released on May 31, 2012.

Unlike Windows 7, which was intended to be a more focused, incremental upgrade to the Windows line, Windows 8 has been "reimagined from the chipset to the user experience" to connect more with the user. It features the Metro interface that is designed for touchscreen input similar to that in Windows Phone and on the Xbox 360. A version of Windows 8, called Windows RT, also adds support for the ARM processor architecture in addition to the previously supported microprocessors from Intel and AMD.

Microsoft Windows is a series of graphical interface operating systems developed, marketed, and sold by Microsoft.

Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Microsoft Windows came to dominate the world's personal computer market, overtaking Mac OS, which had been introduced in 1984.

The most recent client version of Windows is Windows 7; the most recent server version is Windows Server 2008 R2; the most recent mobile version is Windows Phone 7.5.The most recent unstable release is Windows 8.

The term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are generally categorized as follows:

The history of Windows dates back to September 1981, when Chase Bishop, a computer scientist, designed the first model of an electronic device and project "Interface Manager" was started. It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. The shell of Windows 1.0 was a program known as the MS-DOS Executive. Other supplied programs were Calculator, Calendar, Cardfile, Clipboard viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal, and Write. Windows 1.0 did not allow overlapping windows. Instead all windows were tiled. Only dialog boxes could appear over other windows.