Reagan County is a county on the Edwards Plateau in the U.S. state of Texas. As of the 2020 census, its population was 3,385. The county seat is Big Lake. The county is named after John Henninger Reagan (1818–1905), who was the postmaster general of the Confederate States and also a U.S. senator, U.S. representative, and first chairman of the Railroad Commission of Texas.

The Edwards Plateau is a geographic region forming the crossroads of Central, South and West Texas, United States. It is named in honor of Haden Edwards. It is bounded by the Balcones Fault to the south and east; the Llano Uplift and the Llano Estacado to the north; and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area. The plateau, especially its southeast portion, is also known as the Texas Hill Country.