The Zagros Mountains (Koerdisch: Zagros - زاگرۆس, Farsi: رشته كوههاى زاگرس)

up Iran's and Iraq's largest mountain range. They have a total length of 1 500 km from western Iran, on the border with Iraq to the southern parts of the Persian Gulf. The mountain range ends at the Straits of Hormuz. The highest points in the Zagros Mountains are Zard Kuh (4 548 m) and Mt. Dena (4 359 m). The Hazaran massif in the Kerman province forms an eastern outlier of the range, the Jebal Barez reaching into Sistan.

The Zagros Mountains were formed by collision of two tectonic plates — the Eurasian and Arabian Plates. Stresses induced in the Earth's crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone (rock formed by consolidated mud) and siltstone (a slightly coarser-grained mudstone) while leaving harder rocks, such as limestone (calcium-rich rock consisting of the remains of marine organisms) and dolomite (rocks similar to limestone containing calcium and magnesium). This differential erosion formed the linear ridges of the Zagros Mountains.

The depositional environment and tectonic history of the rocks were conducive to the formation and trapping of petroleum, and the Zagros region is an important part of Persian Gulf oil production.

Salt domes and salt glaciers are a common feature of the Zagros Mountains. Salt domes are an important target for oil exploration, as the impermeable salt frequently traps petroleum beneath other rock layers.