London is the capital of both England and the United Kingdom. It is the most populous city in the European Union and the second most populous urban area after Paris. An important settlement for two millennia, London's history goes back to its founding by the Romans. Since its beginnings, London has been part of many movements and phenomena throughout history, including the English Renaissance, the Industrial Revolution, and the Gothic Revival in architecture. The city's core, the ancient City of London, still retains its limited medieval boundaries; but since at least the nineteenth century, the name "London" has also referred to the whole metropolis that has developed around it. Today the bulk of this conurbation forms the London metropolitan region and the Greater London administrative area, with its own elected mayor and assembly.

London is one of the world's most important business, financial, and cultural centres and its influence in politics, education, entertainment, media, fashion and the arts contributes to its status as a major global city. Central London is the headquarters of more than half of the UK's top 100 listed companies (the FTSE 100) and over 100 of Europe's 500 largest companies. The city is a major tourist destination for both domestic and overseas visitors, with annual expenditure by tourists of around £15 billion. London hosted the 1908 and 1948 Summer Olympic Games and will host the 2012 Summer Olympic Games.

Greater London contains four World Heritage Sites: the Tower of London; the historic settlement of Greenwich; the Royal Botanic Gardens, Kew; and the site comprising the Palace of Westminster, Westminster Abbey and St. Margaret's Church.

London currently has a wide range of peoples, cultures, and religions, and over 300 languages are spoken within the city. As of July 2007, it had an official population of 7,556,900 within the boundaries of Greater London making it the most populous municipality in the European Union. As of 2001, the Greater London Urban Area is the second largest in the EU after Paris with a population of 8,278,251, and the metropolitan area is estimated to have a total population of between 12 million and 14 million, the largest metropolitan area in the EU. The public transport network, administered by Transport for London, is one of the most extensive in the world, Heathrow Airport is the busiest airport in the world by international passenger traffic and the air space is the busiest of any city in the world.