MotifMotif (or capitalized MOTIF) is a graphical widget toolkit for building Graphical User Interfaces under the X Window System on UNIX and other POSIX-compliant systems.
It is also an industry standard by the name IEEE 1295. It was used, and still is, as the basic building blocks for the Common Desktop Environment. As of version 2.1 Motif supports Unicode which has made it widely used in several multilingual environments.
Many argue that it is practically obsolete when compared to GTK or Qt (a key indicator is that the major Motif user Sun Microsystems have declared that they will switch over to GTK and GNOME), but it is still used in many legacy systems.