Harmon County is a county in the southwest corner of the U.S. state of Oklahoma. As of the 2020 Census, the population was 2,488, making it the second-least populous county in Oklahoma, behind only Cimarron County. It has lost population in every census since 1930. The county seat is Hollis.

Hollis is a city in and the county seat of Harmon County, Oklahoma, United States. The population was 2,060 at the 2010 census.