Fort Sumner is a village in and the county seat of De Baca County, New Mexico, United States. The population was 1,031 at the 2010 U.S. Census, down from the figure of 1,249 recorded in 2000. Fort Sumner is the spring and fall home of the Columbia Scientific Balloon Facility, and is home to the burial site of famed outlaw of the American West, Billy the Kid, who was shot and killed there in 1881.

De Baca County is a county in the U.S. state of New Mexico. As of the 2020 census, the population was 1,698, making it New Mexico's second-least populous county. Its county seat is Fort Sumner. The county is named for Ezequiel Cabeza De Baca, the second elected Governor of New Mexico.