There were celebrations and protests across the country as the clock counted down to 11 p.m. GMT on Friday, bringing an end to almost half a century of Britain's membership of the EU.
In a speech broadcast on Facebook an hour before Britain's exit, Prime Minister Boris Johnson said the moment represented a "new dawn" for the country after three years of division, delay, and parliamentary deadlock.
"The most important thing to say tonight is that this is not an end but a beginning," Johnson said in a video message filmed inside his 10 Downing St. residence. "This is the moment when the dawn breaks and the curtain goes up on a new act. It is a moment of real national renewal and change."
The UK government projected a countdown clock onto the front of Downing Street in the hour leading up to 11 p.m., while "leave" voters celebrated outside the Houses of Parliament with pro-Brexit politicians like Nigel Farage.
Britain formally left the EU hours after Johnson and his Cabinet met in Sunderland. The city in northeast England was famously the first area of the country to declare a "leave" vote in the 2016 referendum.
This meeting of Johnson and his most senior ministers was designed as a public display of the government's commitment to improve the lives of voters in Brexit-voting areas of the UK outside London and the southeast of England.
Meanwhile, in Brussels, there were historic scenes as EU officials took down Union Jack flags in preparation for Britain's formal departure.