The Zagros Mountains (جبال زاجروس), (رشته كوههاى زاگرس) (Sorani Kurdish: Zagros - زاگرۆس), make 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.
The Kuhrud Mountains form one of the parallel ranges at a distance of approx. 300 km to the east. The area between these two impressive mountain chains is home to a dense human population that lives in the intermediate valleys which are quite high in altitude with a temperate climate. Their rivers, which eventually reach salt lakes, create fertile environments for agriculture and commerce.
Some of the earliest evidence of production has been discovered in the Zagros Mountains; both the settlements of Hajji Firuz Tepe and Godin Tepe have given evidence of wine storage dating between 3500 and 5400 BC.
During early ancient times, the Zagros was the home of peoples such as the Kassites, Guti, and Mitanni, who periodically invaded the Sumerian and/or Akkadian cities of Mesopotamia. The mountains create a geographic barrier between the flatlands of Mesopotamia which is in Iraq and the Iranian plateau.