Upshur County is a county located in the eastern part of the U.S. state of Texas. As of the 2020 census, the population was 40,892. The county seat is Gilmer. The county is named for Abel P. Upshur, who was U.S. Secretary of State during President John Tyler's administration.

Gilmer is a city in, and the county seat of, Upshur County, Texas, United States. It is best known for being the home of the East Texas Yamboree and the birthplace of popular music singers Don Henley of the Eagles band and Johnny Mathis, as well as blues musician Freddie King. Its population was 4,843 at the 2020 census.