ZOG was an early hypertext system developed at Carnegie Mellon University during the 1970s by by Donald McCracken and Robert Akscyn. ZOG, which isn't an acronym for anything, was first started in 1972 as a large database for use in a multiuser environment. ZOG consisted of frames that, subsequently, contained a title, a description, a line containing ZOG system commands, and selections (menu items) that led to other frames.

The ZOG database became fully functional around 1977. In 1982, ZOG had been since been ported from the original IBM mainframe version to the Three Rivers PERQ workstation and was used on the American aircraft carrier USS Carl Vinson. In spite of ZOG's capabilities, it was a text-only system. McCracken and Akscyn later went on to developed KMS, an improved version of ZOG.