The Shammar Mountains () is a mountain range in the northwestern Saudi Arabian province of Ha'il. It includes the AjÃÂ () and Salma subranges.
The Aja Mountains are to an extent made up of granite, whereas the Salma are made up of basalt. The phrase "Hadn formation" was used by Chevremont (1982) to refer to volcanic rocks of the area of Ha'il, and was treated by Hadley and Schmidt (1980) as being part of a silicic and volcaniclastic sequence referred to as the "Shammar group", in a broader, regional context.
The protected area of Jabal Aja is of ecological significance. Two Asiatic cheetahs, the last known in the country, were killed near Ha'il in 1973, and their skins kept near the Imara Palace for a few days.