Payne County is a county located in the U.S. state of Oklahoma. As of the 2020 census, its population was 81,646. Its county seat is Stillwater. The county was created in 1890 as part of Oklahoma Territory and is named for Capt. David L. Payne, a leader of the "Boomers". Payne County comprises the Stillwater, OK Micropolitan Statistical Area.