Ballycroy National Park is located in the Owenduff/Nephin Mountains area of the Barony of Erris in northwest County Mayo, Ireland. It is one of the largest expanses of peatland in Europe, consisting of 117.79 square kilometres of Atlantic blanket bog. It is a unique habitat with a diverse flora and fauna. It was established as a national park on 1 November 1998. The area of the park is a candidate Special Area of Conservation (cSAC) as part of a site known as the Owenduff/Nephin Complex. It is also a Special Protection Area and part of the Natura 2000 network.
The European Union Habitats Directive (92/43/EEC), which was transposed into Irish law in 1997, lists certain habitats and species that the Irish Government was required to designate as SACs to ensure their protection. These habitats include blanket bogs. The bog at Ballycroy is especially important in this regard because it is one of the largest examples of a blanket bog habitat left in Western Europe. Ballycroy was established as a national park on 1 November 1998. It is managed under the State Property Act, 1954.
Blanket bogs, cliffs and river habitats are found in the park. The blanket bog is one of the largest expanses of peatland left in Europe. Conservation of the bog is thus of international importance because of the niches it provides for various species, such as rare species of plants. The Owenduff River is also an important conservation area because it is the only river in Western Europe that still drains a relatively intact and extensive blanket bog system. It is also a very prolific salmon and sea trout river.