Ellensburg is a city in and the county seat of Kittitas County, Washington, United States. It is located just east of the Cascade Range near the junction of Interstate 90 and Interstate 82. The population was 18,666 at the 2020 census. and was estimated to be 18,703 in 2022. The city is located along the Yakima River in the Kittitas Valley, an agricultural region that extends east towards the Columbia River.