The Omo River in southern Ethiopia is the largest Ethiopian river outside the Nile Basin. Its course is entirely contained within the boundaries of Ethiopia, and it empties into Lake Turkana on the border with Kenya. The river is the principal stream of an endorheic drainage basin, the Turkana Basin.

The Lower Valley of the Omo is in the remote southwest corner of Ethiopia, close to the border with Kenya, in the Great Rift Valley.  The site is of immense importance for its hominid fossils, which have contributed immeasurably to our understanding of human origins. These fossils include the remains of Homo gracilis and Australopithicines, as well as the earliest known bone fragments of Homo sapiens, dating from 195,000 years ago.  In addition there are rich beds of other mammal fossils.
The boundaries of the world heritage site are not clear from available documentation, but the UNESCO website implies the inclusion of the 4,068 km2 Omo National Park which occupies the West bank of the river, some 100km north of the point where the Omo river spills into Lake Turkana. The fossil skulls of various mammals, including a hominid skull, are from the area covered by the world heritage site.  They are on display at the Ethiopian National Museum in Addis Ababa.