UK Independence Party leader Nigel Farage announced his resignation on Monday, saying he has achieved his goal by securing a vote for Britain to leave the European Union.
Farage, 52, who has led the right-wing party for 10 years, said he wants to step down to focus on his personal life following his long years of campaigning for a British EU exit, or Brexit.
"During the referendum campaign, I said I want my country back," he told reporters in London. "What I'm saying today is I want my life back, and it begins right now."
"The victory for the Leave side in the referendum means that my political ambition has been achieved," Farage said.
"I came into this struggle from business because I wanted us to be a self-governing nation, not to become a career politician."
Farage said he will continue to comment on British politics and warned that he will no longer constrain himself in interviews.
"In future, I won't be constrained when I answer questions," he said. "The real me will now come out."
UKIP has developed into the "third political force" in Britain, Farage said, following the ruling Conservatives and the largest opposition party, Labour.
His surprise resignation comes at a turbulent time in British politics.
Prime Minister David Cameron offered his resignation the day after the referendum, following his failed campaign for Britain to remain in the EU.
Labour leader Jeremy Corbyn is under intense pressure to resign from Labour lawmakers, while Green Party leader Natalie Bennett also plans to step down.
British Foreign Secretary Philip Hammond late Monday said that informal talks with the EU about Brexit could begin as early as next week. Such discussions would address the eventual relationship between London and Brussels after a British departure from the bloc.
He called for Brussels to compromise on the insistence that there could be no talks before a formal British invocation of Article 50 of the Lisbon Treaty, which sets the rules for a nation leaving the EU. An early engagement in talks would help ease the uncertainty for EU citizens living in Britain.