Bardsey Island lies about 2 miles (3 kilometers) across Bardsey Sound of the Lleyn Peninsula, North Wales.
The island is 1.5 miles (2.5 kilometers) long and, at its widest point, it is just over half a mile (1 kilometer) across. The island mountain rises to a height of 167 meters and the whole island has a surface area of 180 hectares, most of which is farmland.
The island was purchased by the Bardsey Island Trust in 1979 and is managed by the Trust with advice from Natural Resources Wales and CADW. The island is designated a National Nature Reserve, a Site of Special Scientific Interest and is in the Lleyn Peninsula Area of Outstanding Natural Beauty.