Wild Nephin National Park, National park with dark skies in County Mayo, Ireland

Wild Nephin National Park is a protected area in northwest County Mayo covering mountains, blanket bogs, grasslands, and river systems that reach toward the Atlantic coast. It also carries designation as an International Dark Sky Park and a Special Area of Conservation, giving it overlapping layers of protected status.

Ballycroy was established as a national park on 1 November 1998 under the EU Habitats Directive, which Ireland transposed into law in 1997. In 2017, 4,000 hectares of conifer forest and mountain controlled by Coillte were added to the park's 11,000 hectares. The expanded park was renamed Wild Nephin in 2018, with the new lands at Nephin Forest intended for rewilding.

The Bangor Trail cuts through the Nephin Beg mountains along a path where farmers moved their livestock through the uplands for generations. Walking it today means moving through a landscape shaped by that long use, still largely unchanged.

The visitor centre in Ballycroy village, a 700 square metre building overlooking the Atlantic, opened in 2009 and stays open year round apart from certain holidays. It is the orientation point before entering the terrain. The Nephin Beg mountains and blanket bog have no shelter, so bring warm waterproof clothing.

The park's blanket bogs have been storing carbon for thousands of years and are among the oldest living ecosystems on the island. A thin layer of peat can contain organic material that is several thousand years old, still preserved beneath the surface.