The UK has left the European Union after 47 years of membership.
An image of Elizabeth Tower was projected onto 10 Downing Street, and pre-recorded bongs from Big Ben were played at 23:00 GMT.
Prime Minister Boris Johnson hailed a “new dawn” for the UK, as European leaders warn of a tough battle ahead in trade talks.
Pro-Brexit campaigners held a celebration rally in nearby Parliament Square, which was lined with Union flags.