A character in the game Riven, sequel to Myst. He is the villain of the game and turns out to be Atrus' father. He builds a town on an island and has the natives worship him as a god.

Gehn's parents were Aitrus and Ti'ana. Because he was the last of the D'ni (until son Atrus was born), Gehn was not properly trained in the art of Writing. Because of this Gehn developed the hubris which all D'ni were taught to avoid: he believed he was actually creating the worlds he wrote, and thus considered himself a god. In fact, writing the special descriptive Books does not create worlds; it merely creates a link to a world that already exists with the given properties. Riven was always unstable because of Gehn's lack of understanding of how to properly describe worlds, and his changes to the descriptive book teneded to do more harm than good.

Gehn became trapped on Riven when Atrus used the last Myst linking book at the same time he threw it into the Star Fissure, where it was presumed lost forever.