The desert in Argentina centered on Mendoza, San Juan, and San Luis provinces is the Monte Desert.
The Monte is an arid South American region lying entirely within Argentina. It covers broad foothill and intermontane areas east of the Andes, including parts of Catamarca, La Rioja, San Juan, San Luis, Mendoza, La Pampa, Río Negro, and Chubut. Mendoza and San Juan are especially associated with its dry valleys and desert landscapes.
The region is shaped by the Andes’ rain shadow: moist air loses much of its water on the Chilean and Argentine slopes, leaving little precipitation farther east. The Monte is not a perfectly sharp-edged desert; its boundaries blend gradually with the Atacama to the northwest and the Patagonian Desert to the south.
A common mix-up is the Atacama Desert, which lies mainly in northern Chile, while the Monte is Argentine. The Patagonian Desert is farther south and covers a much larger portion of southern Argentina.