Quay County is a county in the state of New Mexico. As of the 2020 U.S. census, the population was 8,746. Its county seat is Tucumcari. The county was named for Pennsylvania senator Matthew Quay, who supported statehood for New Mexico. Its eastern border is the Texas state line, approximately 103.04 degrees west longitude.

Tucumcari is a city in and the county seat of Quay County, New Mexico, United States. The population was 5,278 at the 2020 census. Tucumcari was founded in 1901, two years before Quay County was established.