Windows 8 is the current release of the Windows operating system, produced by Microsoft for use on personal computers, including home and business desktops, laptops, tablets, and home theater PCs. Development of Windows 8 started before the release of its predecessor in 2009. Its existence was first announced at CES 2011, and followed by the release of threepre-release versions from September 2011 to May 2012. The operating system was released to manufacturing on 1 August 2012, and was released for general availability on 26 October 2012.

Windows 8 introduces significant changes to the operating system's platform, primarily focused towards improving its user experience on mobile devices such as tablets to rival other mobile operating systems like Android and iOS, taking advantage of new or emerging technologies like USB 3.0, UEFI firmware, near field communications, cloud computing and the low-power ARM architecture, new security features such as malware filtering, built-in antivirus capabilities, a new installation process optimized for digital distribution, and support for secure boot (a UEFI feature which allows operating systems to bedigitally signed to prevent malware from altering the boot process), the ability to synchronize certain apps and settings between multiple devices, along with other changes and performance improvements. Windows 8 also introduces a new shell and user interface based on Microsoft's "Metro" design language, featuring a new Start screen with a grid of dynamically updating tiles to represent applications, a new app platform with an emphasis on touchscreen input, and the new Windows Store to obtain and/or purchase applications to run on the operating system.

Windows 8 was released to mixed reception—although reception towards its performance improvements, security enhancements, and its improved support for touchscreen devices was positive, the new user interface of the operating system has been widely criticized for being confusing and having a steep learning curve (especially when used with a keyboard and mouse instead of a touchscreen). Despite these shortcomings, 40 million Windows 8 licenses were sold during its first month of availability, mostly to original equipment manufacturers (OEMs).