A policy and land use designation used in land use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding, or neighbouring, urban areas.
In UK town planning, the green belt is a policy for controlling urban growth. The idea is for a ring of countryside where urbanisation will be resisted for the foreseeable future, maintaining an area where agriculture, forestry and outdoor leisure can be expected to prevail. The fundamental aim of green belt policy is to prevent urban sprawl by keeping land permanently open, and consequently the most important attribute of green belts is their openness.
It was first proposed around London by the Greater London Regional Planning Committee in 1935. The Town and Country Planning Act 1947 then allowed local authorities to include green belt proposals in their development plans.