The term Texas River is composed of five rivers: the Sabine, Pecos, BRAZOS, Nueces, and San Antonio. The Sabine River is a river in East Texas that forms part of the boundary between Texas and Louisiana. The Pecos River is a river in West Texas that flows into the Rio Grande. The BRAZOS River is the longest river in Texas and runs through the center of the state. The Nueces River is a river in South Texas that flows into the Gulf of Mexico. The San Antonio River is a river in South Central Texas that flows through the city of San Antonio.