OpenWindows is a discontinued desktop environment for Sun Microsystems workstations which combined a display server supporting the X Window System protocol, the XView and OLIT toolkits, the OPEN LOOK Window Manager (olwm), and the DeskSet productivity tools; earlier versions of OpenWindows also supported the NeWS protocol.

OpenWindows 1.0 was released in 1989 as a separately licensed addition to SunOS 4.0,[1] replacing the older SunView (originally "SunTools") windowing system.

It was still called OpenWindows (now version 3.3), but the NeWS protocol was replaced by support for Display PostScript.

The alliance chose the Motif look and feel as its standard, and Sun announced it would phase out OpenWindows in favor of the new COSE desktop environment, which came to be known as CDE.

Some OpenWindows applications were never released as open source by Sun, so some of these have been rewritten and some are still missing.