The New Microsoft Windows Vista is the next major version of Microsoft Windows, the proprietary operating system developed by Microsoft. Prior to the announcement of the Vista name on July 22, 2005, it was known by its codename Longhorn, after the Longhorn Saloon, a popular bar in Whistler, British Columbia. Microsoft released all Windows Vista products on January 30th, 2007 including both business and consumer editions.

After "Longhorn" was renamed to Windows Vista, an unprecedented (for Microsoft) beta-test program was started, which has involved hundreds of thousands of volunteers and companies. In September 2005, Microsoft started releasing regular Community Technology Previews (CTP) to beta testers. The first of these was build 5219, distributed among 2005 PDC attendees, and has been released to Microsoft Beta testers and MSDN subscribers. Subsequent CTPs have introduced most of the planned features for the final product, as well as a number of changes to the user interface, based in large part on feedback from beta testers. Windows Vista was deemed "code-complete" with the release of build 5308 CTP, released on February 22, 2006, and much of the remainder of work between that build and the final release of the product will focus on stability, performance, application and driver compatibility, and documentation. Jim Allchin stated in an interview there will be no "Release Candidates" as with previous versions of Windows; they will instead continue shipping CTPs until the product is ready.

Windows Vista has many new features, such as an updated graphical user interface dubbed Aero, improved searching technology, a number of new security features, and completely redesigned networking, audio, print and display sub-systems. Vista also aims to increase the level of communication between machines on a home network using peer-to-peer technology, making it easy to share files, password settings, and digital media between computers and devices. For developers, Vista also has an entirely new development API, called WinFX, based on the .NET framework, which aims to make it significantly easier for developers to write high-quality applications than with WinFX's predecessor, Win32. The Enterprise edition of Vista includes Microsoft's Virtual PC technology, so that line-of-business applications that are incompatible with Vista can still be used in a fashion similar to how Mac OS X's "Classic" mode supported older Macintosh applications.