The Greenbelt is a ring of land, formerly surrounding the city of Ottawa, in which real estate development is not permitted. The Greenbelt is maintained by the National Capital Commission (NCC). It was created when it was worried urban sprawl would destroy the pristine areas surrounding the city. The goal of the project is to create an urban forest. To date, the Ottawa Greenbelt is among the largest urban parks in the world.

Due to the January 1, 2001 amalgamation of Ottawa with several surrounding cities, the Greenbelt no longer surrounds Ottawa, but rather it forms an arc through the inside of the city. In addition, parts of the former suburban cities of Nepean and Gloucester were inside the Greenbelt as they straddled the boundary.

To some degree, the Greenbelt was a failure; many suburban areas have leapfrogged over and developed beyond the Greenbelt, namely Kanata in the west end (which has almost overlapped the former rural community of Stittsville), Orleans in the east end (which was, before 2001, partly in the city of Gloucester and partly in the city of Cumberland), and Barrhaven in the southwest (part of South Nepean). In addition, new developments are starting to form in the southeast, along Riverside Drive and Bank Street.