Río de Oro is a geographic region located in the southern part of Western Sahara. Historically, it served as one of the two primary territories, along with Saguia el-Hamra, that constituted the Spanish province of Spanish Sahara following 1958. The area was established as a Spanish colonial possession during the late 19th century.
The name Río de Oro is derived from an east–west river that was originally intended to flow through the region. However, this water source is believed to have either disappeared underground or dried out completely, becoming a wadi.