Bannon was CEO of the Trump campaign, and his appointment as chief strategist and senior counselor to the president was one of Trump's first personnel decisions after winning the election. The announcement drew massive criticism due to Bannon's history of inflammatory ultra-conservative views. 

In January 2017, Trump added Bannon to the National Security Council's Principals Committee, a small group of advisors that considers national security policy issues. The decision spurred critics to question whether Bannon had too much power in the White House. 

But in April 2017, a White House memo revealed that Bannon had been removed from the NSC's Principals Committee.

Bannon feuded with other members of the president's inner circle, including Mr. Trump's son-in-law and adviser Jared Kushner. Bannon's tumultuous tenure at the White House ended on Aug. 18, 2017.

Bannon said that a 2016 Trump Tower meeting between Donald Trump Jr., Jared Kushner, Paul Manafort and a Russian lawyer was "treasonous" and "unpatriotic," according to the book "Fire and Fury," published in January 2018.

The book also quoted Bannon as saying that investigators looking into collusion with Russia would "crack Don Junior like an egg on national TV."

President Trump responded with a blistering statement that said in part: "When [Bannon] was fired, he not only lost his job, he lost his mind."

From 2012 to 2016, Bannon was the chairman of Breitbart News, an ultra-conservative website known for its provocative views.

Under Bannon's leadership, the website became even more inflammatory. Bannon declared it "the platform for the alt-right" in an interview in July 2016.

Critics see Bannon's work as aligned with supporters of white nationalism and white supremacy.

The alt-right is defined by the Southern Poverty Law Center as "a set of far-right ideologies, groups and individuals whose core belief is that 'white identity' is under attack by multicultural forces using 'political correctness' and 'social justice' to undermine white people and 'their' civilization."

Shortly after Trump took office, Bannon called the media the "opposition party," adding: "The media should be embarrassed and humiliated and keep its mouth shut and just listen for a while."

Bannon was an investment banker at Goldman Sachs for five years before starting Bannon & Co., a small bank that focused on media deals.

A deal negotiated by Bannon & Co. earned the firm a share of profits from several TV shows, including the hit series "Seinfeld."

From 1993 to 1995, Bannon ran Biosphere 2, an Arizona research facility encased in glass and designed to mimic Earth's environment. The facility is now owned by the University of Arizona. 

An employee of Biosphere 2 sued the company for breach of contract, claiming that Bannon called her a "29-year-old bimbo," and said he would "kick her a**." He admitted to making the statements during a pretrial interview.

A jury reportedly found in favor of the employee, while another lawsuit with Biosphere 2 officials was settled. 

Bannon has been married and divorced three times. He has one daughter with his first wife, and twin daughters with his second wife. 

One of his ex-wives accused him of making anti-Semitic remarks and committing domestic violence. Bannon pleaded not guilty to misdemeanor domestic violence charges, which were eventually dropped, according to The New York Times. 

Bannon was born in Norfolk, Virginia, in 1953. "I come from a blue-collar, Irish Catholic, pro-Kennedy, pro-union family of Democrats," Bannon told Bloomberg in October 2015. 

While talking about why liberal women are not fans of conservative women like Sarah Palin, Bannon said: "... there are some unintended consequences of the women's liberation movement ... That, in fact, the women that would lead this country would be pro-family, they would have husbands, they would love their children.

"They wouldn't be a bunch of dykes that came from the Seven Sisters schools up in New England. That drives the left insane and that's why they hate these women," he continued. 

Bannon has produced conservative-leaning documentaries including "Occupy Unmasked," a critique of the Occupy Wall Street movement; "The Undefeated," about Sarah Palin; and some dramas like "The Indian Runner," which starred Sean Penn. He has writing and directing credits on half of them, according to the movie database IMDB.

In 2006, Bannon persuaded Goldman Sachs to invest $60 million in Internet Gaming Entertainment, which encouraged players to pay real money for virtual goods in the video game World of Warcraft.

The company went downhill after a Warcraft player sued it, alleging it was "substantially impairing" gamers' enjoyment, according to WIRED.

Bannon graduated from Virginia Tech with a bachelor's degree in urban planning in 1976. 

He also holds a master's degree from Georgetown University and received his M.B.A. from Harvard. 

Bannon helped to write President Trump's inaugural address as well as the travel ban he rolled out in January in an attempt to bar travel from seven predominantly Muslim countries to the U.S. and to halt refugees from entering the country.

A U.S. district judge ruled against the travel ban after two states filed lawsuits challenging it. In February 2017, a federal appeals court refused to reinstate it. 

Bannon was in the Navy for seven years, spending a portion of that time at the Pentagon, where he served as a special assistant to the Chief of Naval Operations.