Ballycroy National Park, Co. Mayo was established on 1st November 1998 and consists of c.11,779 hectares of Atlantic blanket bog in the Owenduff/Nephin Beg area of North West Mayo. The area contains some of the most important blanket bog in Europe. Blanket bogs are included in Annex 1 of the Habitats Directive as a priority habitat type of Community interest the conservation of which requires the designation of Special Areas of Conservation. Ireland's western blanket bogs are the most important remaining in Western Europe and north-west Mayo contains some of the most extensive examples of this habitat type.
The Owenduff area in the Nephin Mountains in particular is a wild and remote area of blanket bog, cliffs and river habitats containing some rare species of plants. The area is also important as a roosting, feeding and breeding site for certain migratory species, including some species such as the Greenland White-Fronted Goose, which are listed in Annex 1 of the Birds Directive. The Owenduff River is of international importance in conservation terms and it is the last river in Western Europe, which drains a relatively intact, extensive blanket bog system. The scenery and wilderness qualities of this area are outstanding. The area of the proposed National Park is a candidate Special Area of Conservation and part of the Natura 2000 network.