The Sierra Diablo is a small mountain range in the US state of Texas, extending north and south along the border between Hudspeth and Culberson counties.

[1] The surface of the range slopes gently westward from its crest, but to the east, north, and south there are abrupt escarpments as high as 2,000 feet.

[2]: 1 The range contains the Sierra Diablo Wildlife Management Area, designated in 1945 to conserve the last remaining desert bighorn sheep in Texas.

[2]: 2 Indigenous Lipan Apache people of the region were driven away and killed in the Battle of the Diablo Mountains in 1854 under the command of John George Walker.

A last conflict of the Texas–Indian wars took place at Sierra Diablo in 1880, with Apache under the command of Victorio versus Texas Rangers under George W. Baylor.