The Frontier Closed Area (Chinese: 邊境禁區), established by the Frontier Closed Area Order, 1951, and 1984 is a regulated border zone in Hong Kong that extended inwards from the border with Mainland China.

Established to prevent illegal migrants and other illegal activities from Mainland China and elsewhere by land and sea, the closed area is fenced along its perimeter to serve as a buffer between the closed border and the rest of the territory patrolled and controlled by Hong Kong Police Force and its Marine Region and the Immigration Department at land and sea. Developments are tightly controlled within the area, leading to less construction and causing most of the area to become a natural habitat for animals and plants.

For anyone to enter the area, a Closed Area Permit is required from the Hong Kong Police Force, unless crossing the land boundary through the Frontier Closed Area with a valid travel document by land and/or sea.