The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico. The length of the Rio Grande is 1,896 miles (3,051 km), making it the 4th longest river in North America by main stem. It originates in south-central Colorado, in the United States, and flows to the Gulf of Mexico. The Rio Grande drainage basin (watershed) has an area of 182,200 square miles (472,000 km²); however, the endorheic basins that are adjacent to and within the greater drainage basin of the Rio Grande increase the total drainage-basin area to 336,000 square miles (870,000 km²).

The Rio Grande with its fertile valley, along with its tributaries, is a vital watersource for seven US and Mexican states, and flows primarily through arid and semi-arid lands. After traversing the length of New Mexico, the Rio Grande becomes the Mexico–United States border, between the U.S. state of Texas and the northern Mexican states of Chihuahua and Coahuila, Nuevo León and Tamaulipas; a short segment of the Rio Grande is a partial state-boundary between the U.S. states of New Mexico and Texas. Since the mid–twentieth century, only 20 per cent of the Rio Grande's water reaches the Gulf of Mexico, because of the voluminous consumption of water required to irrigate farmland (e.g. the Lower Rio Grande Valley) and to continually hydrate cities (e.g. Albuquerque); such water usages are additional to the reservoirs of water retained with diversion dams. 260 miles (418 km) of the river in New Mexico and Texas are designated as the Rio Grande Wild and Scenic River.