A frontier is the political and geographical areas near or beyond a boundary. The term came from French in the 15th century, with the meaning "borderland"—the region of a country that fronts on another country (see also marches).

The word "frontier" also means a region at the edge of a settled area, especially in North American development. It is a transition zone where explorers, pioneers and settlers were arriving. A frontier can also be referred to as a "front".