Mountain ranges (mountain systems; iron mountains, misty range, the penitents), are a series of mountains arranged in a chain and connected by elevated land. Ranges are often created through the action of plate tectonics. Mountain ranges may feature a series of peaks, valleys, and mountain passes. There may be cave systems that connect various regions with underground rivers and streams. Temples, watchtowers, castles, or ski resorts may be located on their surface. There may be gondolas, train routes, and mine cart tracks connecting locations on the mountain or crossing it.

Mountain ranges are featured heavily in fictional cartography, where they may act as important boundaries between the frontier and the wilderness or as borders between countries. Ranges have a drastic impact on the local climate. Clouds traveling over mountains will release their moisture as they travel upwards in elevation. This often causes jungles or forests to form on the windward side of the mountain range. On the other side of the range will be a rain shadow, and will often be the location of a desert.

Mountain ranges are often formed at the boundaries of tectonic plates.