OPEN LOOK or OpenLook was an early graphical user interface (GUI) specification developed by Sun Microsystems and AT&T in the early 1990s for UNIX workstations. It had its origins in SunOS 2.1, SunView and Sun's Motorola 68000-based UNIX workstations. OpenLook was distinguised by its oval-shaped buttons, triangle pull down menus and pushpins which allowed dialog boxes and palettes to stay visible. Because it was a specification at the user level, it could actually be implemented in different ways underneath -- using X Windows or Sun's NeWS toolkit. The specification was a collaboration between Sun and AT&T, which had an alliance back to develop UNIX and graphical toolkits. OpenLook had a useable pallete of 256 colours.

In the early 1990s, its main competitor was the OSF Motif GUI or the vanilla X Windows TWM window manager and Athena widgets. At the time, Motif was backed by the rest of the workstation industry, such as IBM, Hewlett-Packard and Digital Equipment Corporation.

In an attempt to create an API to make applications GUI independent, Sun and AT&T tried to develop the awkwardly named MoOLIT, which was a Motif-OpenLook library with common GUI features such as boxes, menus, lists, buttons, etc., but allowed users to choose which GUI they wanted at runtime. It was not considered a very successful products and was not widely used.

Shortly after the industry had made its intentions clear, OpenLook was eventually dropped by Sun in favor of Common Desktop Environment and Motif.