Brazos Santiago Pass is a natural coastal landform located in the Lower Laguna Madre and Lower Rio Grande Valley on the furthest southern beach terrain of the Texas Gulf Coast. The seacoast passage is interpolated by barrier islands encompassing the southern Brazos Island and the northern South Padre Island. The natural ocean inlet has a shoreline distance on Brazos Island of 7.5 miles (12.1 km) to the Rio Grande often entitled as the Mexico–United States border.