Omak Lake is a saline endorheic lake in the U.S. state of Washington, within the Greater Omak Area. The lake covers at an elevation of and is fed by three small creeks. With a volume of and depth of , Omak is the largest saline lake in Washington.
The name Omak comes from the Okanogan placename [umák].
Omak Lake occupies a former channel of the Columbia River. The Okanagan people once believed that Omak Lake was inhabited by spirits, and avoided the area.