St Kilda, Scotland in the context of National Trust for Scotland

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. It is the westernmost point in Wales other than the isolated rocks on which the Smalls Lighthouse stands. Grassholm is known for its huge colony of northern gannets; the island has been owned since 1947 by the Royal Society for the Protection of Birds, and is one of its oldest reserves. It reaches 42 metres (138 ft).

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 per cent of the world population. The turbulent sea around Grassholm is a good feeding area for porpoises and bottlenose dolphins.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Sites are places of importance to cultural or natural heritage as described in the UNESCO World Heritage Convention, established in 1972. Cultural heritage consists of monuments (such as architectural works, monumental sculptures, or inscriptions), groups of buildings, and sites (including archaeological sites). Natural features (consisting of physical and biological formations), geological and physiographical formations (including habitats of threatened species of animals and plants), and natural sites which are important from the point of view of science, conservation or natural beauty are defined as natural heritage. The United Kingdom ratified the convention on 29 May 1984, making its sites eligible for inclusion on the list.

There are 35 World Heritage Sites in the United Kingdom and the British Overseas Territories. Out of these sites, one site is located in both England and Scotland (the Frontiers of the Roman Empire), eighteen are exclusively in England, seven in Scotland, four in Wales, two in Northern Ireland, and one in each of the overseas territories of Bermuda, Gibraltar, the Pitcairn Islands, and Saint Helena. The first sites in the UK to be inscribed on the World Heritage List were Giant's Causeway and Causeway Coast; Durham Castle and Cathedral; Ironbridge Gorge; Studley Royal Park including the Ruins of Fountains Abbey; Stonehenge, Avebury and Associated Sites; and the Castles and Town Walls of King Edward in Gwynedd in 1986. The most recent site listed was Gracehill, as a part of transnational site Moravian Church Settlements, in 2024. Among the 35 sites, 29 are listed for their cultural significance, five for their natural significance, and one, St Kilda, for both. In addition, there are five sites on the tentative list. The UK has served on the World Heritage Committee once.

Soay (Scottish Gaelic: Soaigh) is an uninhabited islet in the St Kilda archipelago, Scotland. The name is from Old Norse Sauðey, meaning "island of sheep". The island is part of the St Kilda World Heritage Site and home to a primitive breed of sheep. Excluding Rockall, it is the westernmost point of the United Kingdom.

The Rockall Trough (Scottish Gaelic: Clais Sgeir Rocail) is a deep-water bathymetric feature to the northwest of Scotland and Ireland, running roughly from southwest to northeast, flanked on the north by the Rockall Plateau and to the south by the Porcupine Seabight. At the northern end, the channel is bounded by the Wyville-Thomson Ridge, named after Charles Wyville Thomson, professor of zoology at the University of Edinburgh and driving force behind the Challenger Expedition. At the southern end, the trough opens into the Porcupine abyssal plain. The Rockall Basin (also known as the Hatton Rockall Basin) is a large (approximately 800 by 150 kilometres (500 by 90 mi)) sedimentary basin that lies beneath the trough. Both are named after Rockall, a rocky islet lying 301.4 km (187.3 mi) west of St Kilda.

Features of the Rockall Plateau have been officially named after features of Middle-earth in the fiction of J. R. R. Tolkien, e.g. Eriador Seamount, Rohan Seamount, Gondor Seamount, Fangorn Bank, Edoras Bank, Lorien Knoll, Isengard Ridge.

Hirta (Scottish Gaelic: Hiort) is the largest island in the St Kilda archipelago, on the western edge of Scotland. The names Hiort (in Scottish Gaelic) and Hirta (historically in English) have also been applied to the entire archipelago. Now without a permanent resident population, the island had nearly all of St Kilda's population of about 180 residents in the late 17th century and 112 in 1851. It was abandoned in 1930 when the last 36 remaining inhabitants were evacuated to Lochaline on the mainland.

The National Trust for Scotland owns the entire archipelago. It became one of Scotland's six World Heritage Sites in 1986 and is one of the few in the world to hold mixed status for both its natural and cultural qualities. Visits to the island are encouraged during months when the few facilities for tourists are open.

Dùn is an island in St Kilda, Scotland. It is nearly 1 mile (1.6 kilometres) long. Its name simply means "fort" in Scottish Gaelic (for more information, see "dun"), but the fort itself has been lost – old maps show it on Gob an Dùin (NF109972), which is at the seaward end.

Though Dùn is almost joined to Hirta at Ruiaval, the two islands are separated by Caolas an Dùin (the straits of Dùn). This prevents Soay sheep from Hirta straying onto the island, and thus it is more vegetated.

Boreray (Scottish Gaelic: Boraraigh; Scots: Boreray) is an uninhabited island in the St Kilda archipelago in the North Atlantic.

The Soay sheep is a breed of domestic sheep (Ovis aries) descended from a population of feral sheep on the 100-hectare (250-acre) island of Soay in the St Kilda Archipelago, about 65 kilometres (40 mi) from the Western Isles of Scotland. It is one of the Northern European short-tailed sheep breeds.

It remains physically similar to the wild ancestors of domestic sheep, the Mediterranean mouflon and the horned urial sheep of Central Asia. It is much smaller than modern domesticated sheep but hardier, and is extraordinarily agile, tending to take refuge amongst the cliffs when frightened. Soays may be solid black or brown, or more often blonde or dark brown with buffish-white underbelly and rump (known as lachdann in Scottish Gaelic, which is cognate to the Manx loaghtan); a few have white markings on the face.

Harris (Scottish Gaelic: Na Hearadh, pronounced [nə ˈhɛɾəɣ] ) is the southern and more mountainous part of Lewis and Harris, the largest island in the Outer Hebrides, Scotland. Although not an island itself, Harris is often referred to in opposition to the Isle of Lewis as the Isle of Harris, which is the former postal county and the current post town for Royal Mail postcodes starting HS3 or HS5.

The civil parish of Harris is considered to include St Kilda, a now uninhabited archipelago 40 miles (65 kilometres) west-northwest of North Uist, and the uninhabited islet Rockall, which is 230 miles (370 kilometres) west of North Uist.