The Greenbelt is a 203.5-square-kilometre (78.6 sq mi) protected green belt traversing Ottawa, Ontario, Canada. It includes green space, forests, farms, and wetlands from Shirleys Bay in the west and to Green's Creek in the east. It is the largest publicly owned green belt in the world and the most ecologically diverse area in Eastern Ontario. The National Capital Commission (NCC) owns and manages 149.5 square kilometres (57.7 sq mi), and the rest is held by other federal government departments and private interests. Real estate development within the Greenbelt is strictly controlled.

A green belt is a policy, and land-use zone designation used in land-use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighboring 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 essence, a green belt is an invisible line designating a border around a certain area, preventing development of the area and allowing wildlife to return and be established.