Clarence “Skip” Ellis (born May 11, 1943, in south Chicago, Illinois) is an American computer scientist, a professor of computer science at the University of Colorado at Boulde.
While at Xerox’s Palo Alto Research Labs, Ellis helped to develop the icon-based GUI, which later became the basis for Apple’s Macintosh and Microsoft’s Windows operating systems. He has also worked at AT&T/Bell Labs, IBM, and several large government research facilities. Ellis has lectured at MIT, Stanford University, the University of Texas, and internationally in Taiwan and Paris. As of 2008, Ellis is currently a professor of computer science at the University of Colorado at Boulder.