Lorestan province is a province of western Iran in the Zagros Mountains. In the wider sense it consists of that part of western Iran coinciding with the province of Ilam and extending on a northwest to southeast axis from Kermanshah to Fars. The terrain consists chiefly of mountains, with numerous ranges, part of the Zagros chain, running northwest to southeast. 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.

Climatically, the province can be divided into three parts: the mountainous regions, experience cold winters and moderate summers. In the central region, the spring season begins from mid-February and lasts till mid May. However, southern areas are under the influence of the warm air currents of Khuzestan, have hot summers and relatively moderate winters. The climate is generally sub-humid continental with winter precipitation, a lot of which falls as snow. Because it lies on the westernmost slopes of the Zagros Mountains, annual precipitation in Lorestan is among the highest anywhere in Iran south of the Alborz Mountains.