A pass is a gap, or break, in high, rugged terrain such as a mountain ridge. A pass forms when a glacier or stream erodes, or wears away, the land between areas of higher terrain. Passes often provide the easiest routes for people to travel across steep mountain ranges. For this reason, they have played an important role throughout human history in migration, trade, and settlement.

Most passes are flat at their summits and have the shape of a saddle. They can consist of very short, steep summits, or expansive valleys that stretch for kilometers. Often, passes sit just above the source of a river fed by precipitation and snowmelt.

Passes are good places to build settlements or defensive outposts because they are usually the only flat land in a mountainous area. This vantage point also makes a pass an easier location to defend against threats or enemies.

In some parts of the world, passes connect different cultures that are separated by the mountains between them. The Khyber Pass, which connects Pakistan and Afghanistan in the Hindu Kush mountains, has served as a key trade route between Central Asia and South Asia for thousands of years. Today, it is the route between the modern cities of Kabul, Afghanistan and Peshawar, Pakistan.

"Pass" may also refer to a channel, or deeper part of a body of water, that allows passage through an otherwise shallow waterway.