The Gran Desierto de Altar is one of the major sub-ecoregions of the Sonoran Desert, located in the State of Sonora, in northwest Mexico. It includes the only active erg dune region in North America. The desert extends across much of the northern border of the Gulf of California, spanning more than 100 kilometres (62 mi) east to west and over 50 kilometres (31 mi) north to south. It constitutes the largest continuous wilderness area within the Sonoran Desert.

The Sonoran Desert is a hot desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States. It is the hottest desert in both Mexico and the United States. It has an area of 260,000 square kilometers (100,000 sq mi).