The Oostvaardersplassen (Dutch pronunciation: [oːstˈfaːrdərsˌplɑsə(n)]) is a nature reserve in the Netherlands, managed by the Staatsbosbeheer (state forestry service).

[7] Before the establishment of the reserve, the dry area was a nursery for willow trees, and in the first year hundreds of seedlings could be found on each square metre.

To avoid this, the park's managers brought in a number of large herbivores to keep the area more open, including Konik horses, red deer and Heck cattle.

The ecosystem developing under their influence is thought to resemble those that would have existed on European river banks and deltas before human disturbance.

The tarpan and aurochs are extinct, but Konik ponies and Heck cattle are able to act as functional equivalents, occupying a similar ecological niche.

[18] In the winter of 2017–2018, almost 3.300 deer, horses and cattle starved to death[19] dividing[20] the Dutch public[21] and leading to demonstrations and individuals feeding hay to the animals despite police arrests.

The "Ecological Main Structure" plan proposes connections between nature reserves in the Netherlands, calling for a corridor to be created toward nearby Horsterwold [nl].

In 2012 the creation of Oostvaarderswold [nl], the 7 × 1 mi connecting corridor between Oostvaardersplassen and the Horsterwold, was stopped, and four members of the regional parliament resigned.