According to reports, Bannon was forced out of the publication by Rebekah Mercer, a major financial patron of Breitbart.
"I'm proud of what the Breitbart team has accomplished in so short a period of time in building out a world-class news platform," Bannon later said of the outlet in a statement on his exit.
Moving forward, Larry Solov, the outlet's chief executive, said in his own statement that the company will now work on a smooth transition for Bannon.
As for staff, reports indicate they've been told to keep mum on the entire ordeal.
The announcement that the 64-year-old Virginian will be jobless comes just days after the early release of "Fire and Fury," Michael Wolff's controversial tell-all book about the Trump administration. In the book, Bannon is quoted as saying a meeting between Donald Trump, Jr. and a Russian lawyer at Trump Tower during the 2016 presidential campaign was "treasonous" and "unpatriotic."
"The three senior guys in the campaign thought it was a good idea to meet with a foreign government inside Trump Tower in the conference room on the 25th floor — with no lawyers. They didn't have any lawyers," Bannon was quoted as saying. "Even if you thought that this was not treasonous, or unpatriotic, or bad sh*t, and I happen to think it's all of that, you should have called the FBI immediately."
In response to Bannon's accusations, Trump released a statement saying that his former adviser had "not only lost his job, he lost his mind."
"Now that Steve is on his own, Steve is learning that winning isn't as easy as I make it look," POTUS wrote. "Steve had very little to do with our historic victory, which was delivered by the forgotten men and women of this country."
"Steve pretends to be at war with the media, which he calls the opposition party, yet he spent his time at the White House leaking false information to the media to make himself seem far more important than he was," the president's statement added.
Bannon was a founding member of Breitbart's board in 2007 and became the media organization's executive chair in March 2012 after founder Andrew Breitbart died from heart failure. He left Breitbart in August 2016 to join Trump's campaign staff as its chief executive, and when Trump took office, Bannon transitioned into the role of White House chief strategist. He would eventually part ways with the Trump administration in August 2017.
Bannon said after departing the White House that he only left to continue to push Trump's agenda from the outside, telling a conference the following month. "I left the White house because Trump needed a wingman outside." Their relationship deteriorated spectacularly as excerpts from Wolff's book came to light.
"I was working at Breitbart when Andrew Breitbart died and Steve Bannon took over," Lee Stranahan, a former Breitbart reporter and now co-host of Fault Lines on Radio Sputnik, told Sputnik. "Steve was an important part of keeping the company going and… was able to build the company into something much bigger before joining the Trump campaign. Unfortunately, he was unable to be successful in the White House and after returning to Breitbart, he has made one bad decision after another. Breitbart News had no real choice but to let him go, and now faces an uncertain future with no-one clearly positioned to take his place."