The Didessa River (pronounced: ɗeɗ:e:s:a; Afaan Oromo: Dhedheessa) is a river in western Ethiopia. A tributary of the Abay River, it rises in the mountains of Gomma, flowing in a northwestern direction to its confluence where the course of the Abay has curved to its southernmost point before turning northwards at about . The Didessa's drainage area is about 19,630 square kilometers, covering portions of the Benishangul-Gumuz Region and the West Welega Zone of the Oromia Region.