Friends of Bannon said that he "felt liberated since it became clear he was being pushed out", and planned to operate Breitbart as a "killing machine".
The populist-nationalist movement got a lot stronger today," Breitbart News editor-in-chief Alex Marlow said in an announcement.
"Breitbart gained an executive chairman with his finger on the pulse of the Trump agenda."
Bannon has also reportedly met with the billionaire Mercer family - key Republican campaign donors whose support he secured for the 2016 election.
DISMISSAL DETAILED
Press secretary Sarah Huckabee Sanders confirmed the news of Bannon's removal from the White House Friday afternoon, saying chief of staff John Kelly and Bannon had "mutually agreed today would be Steve's last day".
The New York Post reported that Kelly had reviewed West Wing staff and was expected to fire the former Breitbart editor, the voice of the alt-right who had the President's ear.
Bannon had been on the outer with Trump before, but the President now suspects he was one of the main leakers in the administration, trashing his colleagues in the press.
The notoriously thin-skinned president also resented the publicity Bannon had been getting as the supposed mastermind of Mr Trump's campaign and upset victory.
"His departure may seem turbulent in the media, but inside it will be very smooth. He has no projects or responsibilities to hand off," one White House source told Axios.
When asked at his fiery press conference at Trump Tower on Tuesday whether he still had confidence in Bannon, Trump said "well let's see".
The President then sought to minimise the role the right-wing firebrand played in his election win.
"I like Mr Bannon, he's a friend of mine, but Mr Bannon came on very late," Trump said.
"I went through 17 senators, governors and I won all the primaries.
"Mr Bannon came on very much later than that," he said. "He's not a racist, I can tell you that; he's a good person. He actually gets very unfair press in that regard, but we'll see what happens with Mr Bannon."
BANNON ON THE BACK FOOT
Bannon in recent days gave interviews to publications including The New York Times ,where he defended Mr Trump's controversial comments in the wake of the racial violence in Charlottesville, Virginia, last weekend.
The President and senior White House officials were debating when and how to dismiss Bannon.
A person close to Bannon insisted the parting of ways was his idea, and that he had submitted his resignation to the President on August 7 for it to be announced at the start of this week but it was delayed in the wake of Charlottesville.
CNN reports that it was Trump's decision to fire Bannon but that he gave his chief strategist the option to resign.
Bannon is the latest in a long line of White House staffers to quit or be pushed out by Trump.
WHITE HOUSE CASUALTY LIST
The hiring of Anthony Scaramucci as communications director set off a chain reaction of staff changes in late July.
Press secretary Sean Spicer quit as a result of that appointment and Scaramucci's allegations that chief of staff Reince Priebus was a leaker led to Priebus's resignation.
Scaramucci was pushed out about a week later after a expletive-laden rant he made to a New Yorker journalist was published.
"I'm not Steve Bannon, I'm not trying to suck my own c**k. I'm not trying to build my own brand off the f***ing strength of the president. I'm here to serve the country," Scaramucci said.
Scaramucci had replaced Mike Dubke as communications director, a position he held for only a couple of months.
During the week it was announced that one of Trump's youngest staffers, 28-year-old Hope Hicks, who was his press secretary during the campaign, would take over as communications director while a permanent replacement was being found.
