Views of Grassholm 1988 from DWT 'Balmoral' Cruise.

Grassholm (Welsh: Gwales or Ynys Gwales) or Grassholm Island is a small uninhabited island situated 13 kilometres (8 mi) off the southwestern Pembrokeshire coast in Wales, lying west of Skomer, in the community of Marloes and St Brides.

Grassholm National Nature Reserve is the third most important site for gannets in the world, after two sites in Scotland: St Kilda and Bass Rock. It serves as a breeding site for 39,000 pairs of the birds, and supports around 10 percent of the world population. The turbulent sea around Grassholm is a good feeding area for porpoises and bottlenose dolphins.

The northern gannet was previously hunted for food in certain parts of its range, and although that practice still continues in the Outer Hebrides of Scotland and the Faroe Islands, the bird faces few other natural or man-made threats. Since its population is growing, the International Union for Conservation of Nature considers it a least-concern species. Because it is both a conspicuous and a common bird, it is referred to in several ancient myths and legends.