Harper County is a county located in the U.S. state of Oklahoma. As of the 2020 census, the population was 3,272, making it the third-least populous county in Oklahoma. The county seat is Buffalo. It was created in 1907 from the northwestern part of Woodward County, and named for Oscar Green Harper, who was clerk of the Oklahoma Constitutional Convention.

Buffalo is a town and county seat of Harper County, Oklahoma, United States. As of the 2020 census, the town’s population was 1,039. It was named after the Buffalo Creek valley, in which it is located.