Moses Lake is a city in Grant County, Washington, United States. The population was 20,366 as of the 2010 census. Moses Lake is the largest city in Grant County. The city anchors the Moses Lake Micropolitan area, which includes all of Grant County and is part of the Moses Lake-Othello combined statistical area.
Moses Lake, on which the city lies, is made up of three main arms over 18 miles (29 km) long and up to one mile (1.6 km) wide. It is the largest natural body of fresh water in Grant County and has over 120 miles (190 km) of shoreline covering 6,500 acres (2,600 ha). Before it was dammed in the early 1900s and then incorporated into the Columbia Basin Project, Moses Lake was a smaller shallow lake. To the south of the town is the Potholes Reservoir and the Columbia National Wildlife Refuge that has a number of seep lakes and vast amounts of migratory birds and other fauna natural to the area.
Before the construction of Grand Coulee Dam on the Columbia River in 1941 and Moses Lake Army Air Base in 1942 the area was largely barren. Native Americans knew the area as Houaph, which meant willow.