Kay County is a county located in the U.S. state of Oklahoma. As of the 2020 census, its population was 43,700. Its county seat is Newkirk, and the largest city is Ponca City. Kay County comprises the Ponca City micropolitan statistical area. It is in north-central Oklahoma on the Kansas state line. Before statehood, Kay County was formed from the "Cherokee Strip" or "Cherokee Outlet" and originally designated as county "K". Its name means simply that.