Britain has voted to leave the European Union in an historic referendum which has thrown Westminster politics into disarray and sent the pound tumbling on the world markets.
In a closely-fought contest, the Leave camp passed the winning post of 16,757,766 with eight of the 382 voting areas still to declare, heading for an overall majority of 52% to 48%.
Ukip leader Nigel Farage declared that June 23 should "go down in history as our independence day", while Vote Leave's chair, the Labour MP Gisela Stuart, said it was "our opportunity to take back control of a whole area of democratic decisions".
Sterling suffered one of its biggest plunges in the overnight markets, hitting lows last seen in 1985 and losing more than 10% against the US dollar, as traders responded with panic to the prospect of the UK quitting the European Union after 43 years.
With Prime Minister David Cameron expected to address the nation from Downing Street before financial markets opened, Labour said he should "seriously consider his position", while Farage said he should resign immediately after voters rejected his passionately-expressed advice to stay in the EU.
Bank of England Governor Mark Carney is expected to make a statement after Cameron.
As polling stations closed at 10pm on Thursday with polls still predicting a Remain victory, 84 pro-Leave Tories - including Boris Johnson and Michael Gove - handed a letter to Cameron urging him to stay on as leader whatever the result of the referendum.
But as Leave built an increasingly unassailable lead as the night wore on, with victories in the Tory English shires, Labour strongholds in the north, Wales and Midlands, others in his party raised questions about Cameron's future.
Long-standing Eurosceptic John Redwood suggested Tories should wait to see if Cameron was willing to "implement the public will" after a Leave vote.
Redwood said the PM should bring in talent from the Leave side to build "a new government to bind the country together". And Conservative backbencher Jacob Rees-Mogg said a general election in the autumn was "not impossible".
Influential backbencher David Davis said the Prime Minister could stay on for a "couple of years" but should put someone else in charge of negotiations on a new relationship with the EU.