Soay sheep on Hirta, St Kilda, with Cleits

St Kilda (Scottish Gaelic: Hiort) is an isolated archipelago 64 kilometres (40 mi) west-northwest of North Uist in the North Atlantic Ocean. It contains the westernmost islands of the Outer Hebrides of Scotland. The largest island is Hirta, whose sea cliffs are the highest in the United Kingdom and three other islands (Dùn, Soay and Boreray), were also used for grazing and seabird hunting. The islands are administratively a part of the Comhairle nan Eilean Siar local authority area.

St Kilda may have been permanently inhabited for at least two millennia, the population probably never exceeding 180 (and certainly no more than 100 after 1851). The entire population was evacuated from Hirta (the only inhabited island) in 1930. Currently, the only year-round residents are defence personnel although a variety of conservation workers, volunteers and scientists spend time there in the summer months.

The origin of the name St Kilda is a matter of conjecture. The islands' human heritage includes numerous unique architectural features from the historic and prehistoric periods, although the earliest written records of island life date from the Late Middle Ages. The medieval village on Hirta was rebuilt in the 19th century, but the influences of religious zeal, illnesses brought by increased external contacts through tourism, and the First World War all contributed to the island's evacuation in 1930. The story of St Kilda has attracted artistic interpretations, including an opera.

The United Kingdom of Great Britain and Northern Ireland (commonly known as the United Kingdom, the UK or Britain) is a sovereign state located off the north-western coast of continental Europe. The country includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the UK that shares a land border with another sovereign state—the Republic of Ireland. Apart from this land border the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel and the Irish Sea.

The United Kingdom is a unitary state governed under a constitutional monarchy and a parliamentary system, with its seat of government in the capital city of London. It is a country in its own right and consists of four countries: England, Northern Ireland, Scotland and Wales. There are three devolved national administrations, each with varying powers, situated in Belfast, Cardiff and Edinburgh; the capitals of Northern Ireland, Wales and Scotland respectively. Associated with the UK, but not constitutionally part of it, are three Crown Dependencies. The United Kingdom has fourteen overseas territories. These are remnants of the British Empire which, at its height in 1922, encompassed almost a quarter of the world's land surface and was the largest empire in history. British influence can still be observed in the language, culture and legal systems of many of its former territories.