Boris Johnson has promised to work “night and day” to repay the trust of voters after he led the Conservatives to an “historic” election win.
With just one seat left to declare, the Tories have a Commons majority of 76.
Speaking in London, the PM said he had a mandate to take the UK out of the EU next month “no ifs, no buts”.
Jeremy Corbyn has said he will not fight another election as Labour leader after the party was swept aside in its traditional heartlands.
With just one constituency – the Cornish seat of St Ives – left to declare, the Conservatives have 364 MPs, Labour 203, the SNP 48, Liberal Democrats 11 and the DUP eight.
Sinn Fein has seven MPs, Plaid Cymru four and the SDLP has two. The Green Party and Alliance Party have one each.
The Brexit Party – which triumphed in the summer's European Parliament elections – failed to win any Westminster seats.
The Conservative Party's Commons majority is its largest since Margaret Thatcher won a third term in 1987.
In his victory speech, Mr Johnson told activists it was a “new dawn” for the country, echoing comments Labour's Tony Blair made when he won the general election of 1997.
He thanked Labour voters, many of whom, he said, had backed the Conservatives for the first time, vowing to lead a “people's government” and fulfil the “sacred trust” placed in him.
“You may intend to return to Labour next time round, and if that is the case, I am humbled that you have put your trust in me, and I will never take your support for granted,” he said.
“I will make it my mission to work night and day, flat out to prove that you were right in voting for me this time, and to earn your support in the future.”