The Prime Minister said he will step down from his role and a new UK leader will be appointed by October this year.
He said, his voice seeming to break, that he "loved this country" and those who had voted Remain must now work with the rest of the population to ensure the transition was smooth.
"Good morning everyone, the country has just taken part in a giant democratic exercise, perhaps the biggest in our history," said Mr Cameron, speaking outside Number 10 with his wife, Samantha Cameron, at his side.
"We should be proud of the fact that in these islands we trust the people for these big decisions.
"We not only have a parliamentary democracy, but on questions about the arrangements for how we've governed there are times when it is right to ask the people themselves and that is what we have done."
He then announced the result - a decision to end the 43-year relationship with the European Union.
52 per cent of the 72.2 per cent who turned out to vote opted for Brexit, polls have shown.
"The British people have voted to leave the European Union and their will must be respected," said Mr Cameron.
"I want to thank everyone who took part in the campaign on my side of the argument, including all those who put aside party differences to speak in what they believe was the national interest and let me congratulate all those who took part in the Leave campaign for the spirited and passionate case that they made."
"The will of the British people is an instruction that must be delivered. It was not a decision that was taken lightly, not least because so many things were said by so many different organisations."
He said that the British public and its leaders, whichever way they had voted, must "now prepare for a negotiation with the European Union."
"This will need to involve the full engagement of the Scottish, Welsh and Northern Ireland governments to ensure that the interests of all parts of our United Kingdom are protected and advanced," he said.
Then he began to lay out plans for his own removal, defending his legacy as he did so.
"But above all this will require strong, determined and committed leadership," he warned.
"I'm very proud and very honoured to have been Prime Minister of this country for six years.
"I believe we've made great steps, with more people in work than ever before in our history, with reforms to welfare and education, increasing people's life chances, building a bigger and stronger society, keeping our promises to the poorest people in the world and enabling those who love each other to get married whatever their sexuality, but above all restoring Britain's economic strength."
But he said that he would no longer be Prime Minister.
"The country requires fresh leadership to take it in this direction," said Mr Cameron.
"I will do everything I can as Prime Minister to steady the ship over the coming weeks and months, but I don't think it would be right for me to try to be the captain that steers our country to its next destination."
He added that the next Prime Minister would decide when to invoke Article 50, which triggers the legal process of exiiting the EU.
"The Cabinet will meet on Monday, the Governor of the Bank of England is making a statement about the steps that the Bank and the Treasury are taking to reassure financial markets.
"We will also continue taking forward the important legislation that we set before Parliament in the Queen's Speech.
"And I have spoken to Her Majesty the Queen this morning to advise her of the steps that I am taking.
"A negotiation with the European Union will need to begin under a new prime minister and I think it's right that this new prime minister takes the decision about when to trigger Article 50 and start the formal and legal process of leaving the EU.
"I will attend the European Council next week to explain the decision the British people have taken and my own decision.
"The British people have made a choice, that not only needs to be respected but those on the losing side of the argument - myself included - should help to make it work.
"Britain is a special country - we have so many great advantages - a parliamentary democracy where we resolve great issues about our future through peaceful debate, a great trading nation with our science and arts, our engineering and our creativity, respected the world over.
"And while we are not perfect I do believe we can be a model for the multi-racial, multi-faith democracy, that people can come and make a contribution and rise to the very highest that their talent allows.
"Although leaving Europe was not the path I recommended, I am the first to praise our incredible strengths.
"I said before that Britain can survive outside the European Union and indeed that we could find a way.
"Now the decision has been made to leave, we need to find the best way and I will do everything I can to help."
With his voice appearing to break, Mr Cameron said: "I love this country and I feel honoured to have served it and I will do everything I can in future to help this great country succeed."
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