The shadow Brexit secretary will replace Jeremy Corbyn as the party leader with Angela Rayner as his deputy.
Sir Keir Starmer has been elected to replace Jeremy Corbyn as the leader of the UK's main opposition party.
The shadow Brexit secretary has secured 56.2% of the first round of voting, which is enough to knock his rivals, Rebecca Long-Bailey and Lisa Nandy, out of the race.
Meanwhile, Angela Rayner has also won her deputy leadership contest with 52.6% of votes.
In a statement, Starmer said it was the "honour and privilege of my life" to be elected, and promised to lead the party into a "new era, with confidence and hope".
He then paid tribute to Corbyn and promised to "tear out" from the "roots" any anti-semitism in the party - an issue that plagued his predecessor.
"I want to pay tribute to Jeremy Corbyn, who led our party through some really difficult times, who energised our movement and who's a friend as well as a colleague," he said.
"And to all of our members, supporters and affiliates I say this - whether you voted for me or not, I will represent you, I will listen to you and I will bring our party together.
"But we have to face the future with honesty.
"Anti-semitism has been a stain on our party. I have seen the grief that its brought to so many Jewish communities. On behalf of the Labour Party, I am sorry.
"I will tear out this poison by irs roots and judge success by the return of Jewish members and those who felt that they could no longer support us."
Turning to the current pandemic, Starmer said the Labour leadership race had come "at a moment like none other in our lifetime" as he noted how it "brought normal life to a halt".
He added: "I can see this happening, people coming together to help the isolated and the vulnerable, checking on their neighbours.
"So mant volunteering for the NHS, millions of people doing their bit to stop this virus and to save lives."
In response former Labour leaders and deputies congratulated their colleague on his new role.
Ed Miliband, who led the party between 2010 and 2015, tweeted his congratulations on a "clear and deserved victory".
"His decency, values and intelligence are what our country needs at this moment of crisis and to lead us to a more equal, fairer and just future."
Tom Watson, the party's former deputy leader, said: "My very best wishes to Keir Starmer. He has great integrity.
"He possesses deep reserves of patience and a first class mind. Above all these qualities, he has a vision of a fairer more equal society."
Who is Sir Keir Starmer?
In his life prior to politics, the 57-year-old worked as a defence barrister for human rights cases, before going on to become director of the UK's Public Prosecutions and Crown Prosecution Service.
He held the role until 2013 and was awarded a knighthood a year later for services to law and criminal justice - hence Sir Keir.
Starmer made his entry to politics a short time later and was elected to represent the London constituency of Holborn and St Pancras in 2015.
A year later, after the UK voted to leave the European Union, he was appointed the country's shadow Brexit secretary.