The Abay River is a river in Ethiopia. Locally it is also known as the Gihon after the river flowing out of the Garden of Eden in the Bible. The river is considered holy by many in Ethiopia. The river forms the first portion of the Blue Nile, and the majority of the water in the Nile originates in the Abay.

The river rises at Lake Tana and loops through northeast Ethiopia before heading into Sudan where it becomes the Blue Nile. After rising at Lake Tana the river flows for some thirty kilometers before plunging over the Tis Issat Water Falls, that are today covered by a hydroelectric dam. The river then travels through a series of deep valleys and canyons. Some of the earliest human remains have been found in this area.