Wild Nephin (Irish: Néifinn Fhiáin, NEFF-in) is a national park in northwest County Mayo, Ireland.

It includes much of the Nephin Beg Mountains and one of the largest expanses of peatland in Europe, consisting of 150 square kilometres of Atlantic blanket bog.

[4] The park is a candidate Special Area of Conservation (cSAC) as part of a site known as the Owenduff/Nephin Complex.

The area is to be managed by the National Parks and Wildlife Service (NPWS) and has been identified as having potential for rewilding.

[8] The area was originally an industrial forest, consisting of lodgepole pine and spruce plantations, with forestry roads throughout.