The Oostvaardersplassen is a nature reserve in the Netherlands, managed by the Staatsbosbeheer. Covering about 56 square kilometres in the province of Flevoland, it is an experiment in rewilding. It is in a polder created in 1968; by 1989, its ecological interest had resulted in its being declared a Ramsar wetland. It became part of Nieuw Land National Park when that was established in 2018.