Great Britain was first inhabited by migrants from the European mainland. Its Iron Age inhabitants are known as the Brythons, a group related to the Celts, much of which was conquered by the Roman Empire to form the province of Britannia. At the Empire’s fall, the southern and eastern parts of the island were taken over by Germanic tribes who became known as the English, while Gaels from Ireland united with the Picts as forerunners of the later Scottish population.  Likewise, the Brythons predated the Welsh.

Subsequent centuries saw Vikings settle in several parts of the island, before the Norman Conquest of 1066 introduced a French ruling elite, which soon also became integral to British life.

Britain was an important part of the Age of Enlightenment, with philosophical and scientific input and a highly influential literary and theatrical tradition. The United Kingdom played a leading role in developing Western ideas of parliamentary democracy with significant contributions to literature, the arts and science. The wealth of the early British Empire, like other Great Powers, was also partly generated by colonial exploitation, including the industrialisation of the slave trade around 1750, with Britain's shipping fleet transporting African slaves to the Americas as part of the infamous triangular trade process. However, on March 25, 1907, British Parliament passed the Abolition of the Slave Trade Act, thusbecoming one of the first nations to permanently prohibit the business of owning and exchanging fellow humans.

After the Industrial Revolution and the defeat of Napoleon, Britain went on to become the dominant world power of the 19th century. At its peak, the British Empire covered almost a quarter of the earth’s surface and encompassed a third of its population, making it the largest empire in history in these respects.

The country played an important role in the development of parliamentary democracy, partly via the emergence of a multi-party system and expansion of suffrage. Developments in science and the arts built on the earlier work of figures such as Isaac Newton and William Shakespeare to bring Britain into the forefront of social, cultural, and technological advancement.

Following successful British campaigns in both World Wars, 1945 saw the emergence of the British Welfare State and one of the world's first and most comprehensive Health Services. The demands of a recovering economy meant that immigrants were welcomed to Britain from all over the Commonwealth, setting in motion the waves of migration that have made multiethnic Britain what it is today.

Although the new postwar limits of Britain's political role were confirmed by the Suez Crisis of 1956, the international ubiquity of the language ensured the continuation of the impact of its literature and culture, while from the 1960s its popular culture found an influence abroad. Following a period of economic stagnation and industrial strife in the 1970s after a global economic downturn, the 1980s saw the premiership of Margaret Thatcher, under whom a marked break with the post-war political and economic consensus saw economic recovery and increasing national self-confidence but with greater social division. The capital city, London, is now arguably the most multicultural in the world.