Moses Lake is a city in Grant County, Washington, United States. The population was 25,146 as of the 2020 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.

Grant County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 99,123. The county seat is Ephrata, and the largest city is Moses Lake. The county was formed out of Douglas County in February 1909 and is named for U.S. President Ulysses S. Grant.