The Conchos River is a tributary of the Rio Grande River but does not exist in the state of Texas. Rather, it flows into the Rio Grande from the Mexican State of Chihuahua and which is called the Rio Conchos in Mexico.

The Conchos River joins the Rio Bravo del Norte (Rio Grande in the US) at the town of Ojinaga, Chihuahau. The Conchos River is the primary river in the state of Chihuahua and is also the largest tributary of the Rio Grande. The Conchos has several reservoirs that make use of its water for agricultural and hydropower uses.

The Conchos rises in the Sierra Madre Occidental in the municipality of Bocoyna, Chihuahua, where it heads east and receives several tributaries along the way. At Valle de Zaragoza municipality, Chihuahua, it is stopped at the La Boquilla Dam, the largest in Chihuahua forming Toronto Lake. It then heads east again, forming Colina Lake and then passes through Camargo, Chihuahua, the main agricultural center in the region, where it receives the Florido as a tributary.

From there, the Conchos heads north, receiving the San Pedro near Delicias, Chihuahua, entering the Chihuahua Desert and cutting a path through it, before turning to the northeast. At Aldama, Chihuahua, it is dammed by the Presa El Granero, then cuts through the Peguis Canyon, before forming a last dam (Toribio Ortega) near Ojinaga. At Ojinaga, it joins the Rio Bravo (Rio Grande in the U.S.).

The Rio Conchos is the eleventh longest river in Mexic

The Rio Conchos contains the only free-flowing large river environment left in the Rio Grande drainage basin. Its river and spring habitat ecosystems are relatively intact and support a highly endemic fish fauna.

Twelve of its forty-seven native fish are endemic, as are twelve of its 46 native reptile and amphibian species. The strong biodiversity has survived in part because the river's ecology has not been affected by channel modifications, otherwise called river engineering.

The Rio Conchos region is significant not only for its surface water biota, but also its specialized spring and cave habitats, which contribute to the region's high endemism. However, conditions are being damaged by industrial pollution, sewage, agricultural wastes, flow regulation, exotic species, and overgrazing. Other threats include poor land and water management practices, such as clear-cutting along the upper Rio Conchos.