Cortland County is a county located in the U.S. state of New York. As of the 2020 census, the population of Cortland County was 46,809. The county seat is Cortland. The county is named after Pierre Van Cortlandt, president of the convention at Kingston that wrote the first New York State Constitution in 1777, and first lieutenant governor of the state. The county is part of the Central New York region of the state.