The Red Mountains are an extensive mountain range in the south of Westeros. They form a barrier between Dorne and the Stormlands to the north-east and the Reach to the west and north-west. There are two major passes through the mountains, the Prince's Pass and the Boneway.
In the books
In the A Song of Ice and Fire novels, the Red Mountains are a formidable obstacle to travel between Dorne and the rest of Westeros. The northern face of the range is scattered with castles designed to defend against Dornish raids. This area is called the Dornish Marches and is part of the Stormlands.
The Red Mountains are noted as being visible from both the Tower of Joy and also Summerhall. They are so-called for the red-colored stone prevalent in the region.