Ellis County is a county located in the U.S. state of Kansas. Its county seat and most populous city is Hays. As of the 2020 census, the county population was 28,934. The county was named for George Ellis, a first lieutenant of the Twelfth Kansas Infantry. Ellis County is the official German Capital of Kansas. German immigrants settled in Hays, Ellis, Victoria, and nearby villages in the 1870s and 1880s.

Walker Army Airfield is an abandoned airfield located north of Interstate 70 in Ellis County, 1 mile northwest of Walker, Kansas or 3 miles northeast of Victoria, Kansas.