Lake Easton is a lake and reservoir along the course of the Yakima River in the U.S. state of Washington. It is located in Township 20N, Range 13E. The Yakima River flows into the lake from the west, and out to the southwest, through the 1929 Easton Diversion Dam. The Kachess River also flows into the lake from the north, where it effectively empties into the Yakima River.