The City of London is the financial centre of London, home to banks, brokers, insurers and legal and accounting firms. A second financial district is developing at Canary Wharf to the east of central London. This is much smaller than City of London, but has equally prestigious occupants, including the global headquarters of HSBC.

Non-financial business headquarters are located throughout central London. Some are in City of London, but more are located further west, in and around Mayfair, St. James's, the Strand and elsewhere. More than half of the UK's top 100 listed companies (the FTSE) are headquartered in central London, and more than 70% in London's metropolitan area. London is a leading global centre for professional services, and media and creative industries.

Tourism is one of the UK's largest industries, and in 2003 employed the equivalent of 350,000 full time workers in London.

While the Port of London is now only the third largest in the United Kingdom — rather than largest in the world, as it once was — it still handles 50 million tonnes of cargo each year. The main docks are now at Tilbury, which is outside the boundary of Greater London.

London's economy generates £116,444 million annually, and accounts for 17% of the UK's Gross Domestic Product; see Economy of the United Kingdom.