Terrell County is a county in the U.S. state of Texas. As of the 2020 census, its population was 760, making it the seventh-least populous county in Texas, and the 37th-least populous county in the nation. Its county seat is the census-designated place of Sanderson; no incorporated municipalities are in the county. The county was named for Alexander W. Terrell, a Texas state senator. Terrell County is one of the nine counties in the Trans-Pecos region of West Texas. It is the setting for Cormac McCarthy's novel No Country for Old Men, and the Academy Award-winning film adaptation of the same name.

Sanderson is a census-designated place (CDP) in and the county seat of Terrell County, Texas, United States. The population was 837 at the 2010 census. Sanderson was created in 1882 as a part of neighboring Pecos County. It became the seat of Terrell County in 1905.