The name Lorestan means "land of the Lurs", and in the wider sense consists of that part of western Iran coinciding with the province of Ilam and extending for about 650 km on a northwest to southeast axis from Kermanshah to Fars, with a breadth of 150–180 km. The terrain consists chiefly of mountains, with numerous ranges, part of the Zagros chain, running northwest to southeast. The central range has many summits which almost reach the line of perpetual snow, rising to 4000 m and more, and it feeds the headwaters of Iran's most important rivers, such as the Zayandeh rud, Jarahi, Karun, Dix, Abi, Karkheh. Between the higher ranges lie many fertile plains and low hilly, well-watered districts.
The highest point of the province is Oshtoran Kooh peak at 4,050 m. The low-lying areas being in the southern most sector of the province, are approximately 500 m above sea level.