Kevin Rudd has stepped down, making Julia Gillard the 27th Prime Minister of Australia.
She told reporters that she was honoured to be in the top job.
Wayne Swan is the new Deputy Prime Minister after the pair were elected by the Labor caucus unopposed.
At ten to ten, Gillard was filmed leaving the meeting, saying there would be a full statement shortly.
After the bloodless coup, Kevin Rudd left the meeting with Defence Minister and ALP veteran John Faulkner at his side.
He later gave an emotional speech.
Small Business Minister Craig Emerson, who had supported Rudd, said the party would get behind her as one.
"Julia Gillard is prime minister and we will all completely and fully support her," he told reporters.
Victorian Premier John Brumby backed Gillard on Sky News.
"I think she'll be a fantastic Prime Minister...I look forward very much to working with herr", she said.
Senior Labor figures earlier said that more than 70 of 112 votes in the Labor caucus would go to Gillard in her bid to defeat Kevin Rudd.
But in the end, the vote was not needed, with Rudd stepping aside.
Ministers split ways
At 9am, Gillard was filmed arriving for the spill, on the verge of being the country's first female Prime Minister after last night telling Rudd she wanted to challenge him.
Environment Minister Peter Garrett was also quoted complimenting Gillard, despite originally backing Rudd.
Foreign Minister Stephen Smith was rumoured to be backing Gillard, while Climate Change Minister Penny Wong was said to also be behind the current Deputy.
Karen Middleton said that MP Jim Turnour, whose seat is under threat, was sticking with Rudd.
Small Business Minister Craig Emerson also threw a rare portfolio behind the PM.
Finance Minister Lindsay Tanner was not involved - and he will reportedly not be moving into the Treasury as he may have hoped, a possible result of professional ill-feeling between himself and Gillard.
Instead, Swan is tipped to keep hold of the portfolio. Sky News reported that he will be travelling to the G20 meeting in Toronto in place of Gillard tomorrow.
Swan's defection to the Gillard camp comes despite backing Rudd to stay on as early as the start of last week.
Unions behind the scene
Analysts say the problem for Gillard may be that the unions were so heavily involved in her running, with the Victorian right urging her to act.
Yesterday, powerful AWU boss Bill Ludwig told the ABC Mr Rudd is "toxic", signalling strong Union support for Gillard.
"We have a better chance of holding government with Julia Gillard that we would have with Rudd," Mr Ludwig said.
Former Premier Peter Beattie backed Ms Gillard, telling the ABC "she is a very talented woman".
Transport Union boss Hughie Williams predicted Ms Gillard would prevail.
"It's quite obvious they have the numbers. We'll have a new prime minister of Australia," Mr Williams said.
But crucially, Gillard also had the support of the right.
And at the core of the challenge is Kevin Rudd's famously poor support base within his party.
A recent Essential poll found the Liberal Party may have a tough time with Gillard, who has made strong ground amongst voters.
Opposition grumble on sidelines
Queensland Senator Barnaby Joyce said the overnight coup attempt against Mr Rudd has been engineered by factional leaders who have taken over the running of the country.
"It is running on auto-pilot in the face of faceless people and faceless men who (were) never elected," Senator Joyce said.
"We're basically realising that the whole direction and metaphor of this government was flawed and we're off to - gosh only knows."
Wilson Tuckey reiterated that the speed of the challenge shows the power of the unions within the Labor Party.