A Green Belt or Greenbelt is a policy or land use designation used in land use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighbouring urban areas. Similar concepts are Greenways or Green Wedges which have a linear character and may run through an urban area instead of around it.

In those countries which have them, development in Green Belt areas is heavily restricted. The objectives of Green Belt policy are to:

• protect natural or semi natural environments;
• improve air quality within urban areas;
• ensure that urban dwellers have access to countryside, with consequent educational and recreational opportunities; and
• protect the unique character of rural communities which might otherwise be absorbed by expanding suburbs.

The effectiveness of Green Belts differs depending on location and country. They can often be eroded by Urban Rural Fringe uses and sometimes, development 'jumps' over the Green Belt area, resulting in the creation of "satellite towns" which, although separated from the city by Green Belt, function more like suburbs than independent communities.

Green Belt policy was pioneered in the United Kingdom, where there are fourteen Green Belt areas, covering 16,716 km², or 13% of England, and 164 km² of Scotland; for a detailed discussion of these, see Green Belt (UK). Other notable examples are the Ottawa and Golden Horseshoe[1], Green Belts in Ontario, Canada. The more general term in the U.S. is green space or greenspace, which may be a very small area such as a park.

The concept of "green belt" has evolved in recent years to encompass not only "Greenspace" but also "Greenstructure", taking into account all urban greenspaces, an important aspect of sustainable development in the 21st. century. The European Commission's COST Action C11 (European Cooperation in the field of Scientific and Technical Research) is undertaking "Case studies in Greenstructure Planning" involving 15 European countries.

An act of the Swedish parliament from 1994 has declared a series of parks in Stockholm and the adjacent municipality of Solna to its north a "national city park" called Ekoparken (the "Eco park"; it stretches from the parks surrounding the royal palaces of Ulriksdal and Haga in Solna, through the Brunnsviken area, down to the former royal hunting grounds of North and South Djurgården).