The Brazos River, called the Rio de los Brazos de Dios by early Spanish explorers (translated as "The River of the Arms of God"), is the longest river in Texas and the 11th longest river in the United States at 2,060 km (1,280 mi) from its headwater source at the head of Blackwater Draw, Curry County, New Mexico to its mouth at the Gulf of Mexico with a 116,000 km² (45,000 sq mi) drainage basin.

The Brazos proper begins at the confluence of its Salt Fork and Double Mountain Fork (two tributaries of which rise west of Lubbock and pass through that city) flowing 840 miles through the middle of Texas. Its main tributaries are the Clear Fork Brazos River, which passes by Abilene and joins the main river near Graham; Bosque River; Little River; Yegua Creek; and Navasota River. Initially running east towards Dallas-Fort Worth, the Brazos turns south, passing through Waco, further south to near Calvert, Texas then past Bryan and College Station, then through Richmond, Texas in Fort Bend County, and into the Gulf of Mexico in the marshes just south of Freeport.