Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the direct successor to Windows NT 3.51, and was released to manufacturing on July 31, 1996, and then to retail on August 24, 1996. It was Microsoft's primary business-oriented operating system until the introduction of Windows 2000. Workstation, server and embedded editions were sold, and all editions feature a graphical user interface similar to that of Windows 95, which was superseded by Windows 98 and could still be directly upgraded by either Windows 2000 Professional or Windows Me.

Mainstream support for Windows NT 4.0 Workstation ended on June 30, 2002, following by extended support ending on June 30, 2004. Windows NT 4.0 Server mainstream support ended on December 31, 2002, with extended support ending on December 31, 2004. Windows NT 4.0 Embedded mainstream support ended on June 30, 2003, followed by extended support on July 11, 2006, with Windows 98 and Windows Me ending support on that date as well. These editions were succeeded by Windows 2000 Professional, the Windows 2000 Server Family and Windows XP Embedded, respectively.

Windows NT 4.0 is the last public release of Windows for the Alpha, MIPS, and PowerPC architectures.