Bannon's new position was listed above the announcement of RNC chair Reince Priebus as Trump's new chief of staff on a statement issued Sunday. It said Bannon and Priebus would be "equal partners."
Under Bannon's leadership, Breitbart espoused anti-Semitic and nationalist views. The site faced regular criticism — including from Democratic nominee Hillary Clinton — for its close ties to the "alt right," an online-based counterculture movement associated with white nationalism.
There was no shortage of reaction to Bannon's ascension to the West Wing.
Evan McMullin, who ran for the White House as an independent and won 21 percent of the vote in Utah:
John Weaver, a top strategist for Ohio Governor John Kasich:
Rep. Keith Ellison (D-MN), who is a top contender to be next chair of Democratic National Committee:
"Mr. Bannon is adored by white supremacists, white nationalists, anti-Semites, neo-Nazis, and the KKK. It's not hard to see why. If the President-elect is serious about rejecting bigotry, hatred, and violence from his supporters, he must rescind Stephen Bannon's appointment," Ellison said in a statement. "This man shouldn't be allowed to visit the White House — let alone run it."
Jonathan Greenblatt, chief executive of the Anti-Defamation League:
Greenblatt praised Trump's choice of Priebus, but bashed Bannon's new role.
"It is a sad day when a man who presided over the premier website of the 'alt-right' — a loose-knit group of white nationalists and unabashed anti-Semites and racists — is slated to be a senior staff member in the 'people's house,'" he added.
Joel Pollak, who worked for Bannon at Breitbart:
Pollak told NBC News that the soon-to-be White House chief strategist was not anti-Semitic, racist or anti-woman.
He called Bannon a champion of a diverse range of conservative voices.
"I think Steve is a national hero," Pollak told NBC News. "From my perspective, in terms of what I believe, I'm an Orthodox Jew, I am an immigrant, I'm married to a black woman, and I live in a liberal city. And Steve saved this country by helping Donald Trump win and restoring balance in the Supreme Court and giving Americans an opportunity to take their government back."
Marion Le Pen, the granddaughter of the founder of France's far-right National Front party:
The Council on American-Islamic Relations:
CAIR National Executive Director Nihad Awad that Bannon's appointment adds fuel to the fire of racial and ethnic hatred and division in America.
"The appointment of Stephen Bannon as a top Trump administration strategist sends the disturbing message that anti-Muslim conspiracy theories and White nationalist ideology will be welcome in the White House," Awad added. "We urge President-elect Trump to reconsider this ill-advised appointment if he truly seeks to unite Americans."
The organization said Bannon "promoted conspiracy theories that "paint a dark and paranoid picture" of American Muslims. Breitbart News traffics in misogynistic and racist stories targeting women, people of color and immigrants."
Congressman Mark Meadows, who represents North Carolina's 11th district:
A spokesman for Harry Reid, the Senate minority leader:
"President-elect Trump's choice of Steve Bannon as his top aide signals that white supremacists will be represented at the highest levels in Trump's White House," Adam Jentleson said. "It is easy to see why the KKK views Trump as their champion when Trump appoints one of the foremost peddlers of white supremacist themes and rhetoric as his top aide ... Sworn testimony in a court case alleged that Bannon committed violent domestic abuse and stated that he 'didn't want the girls going to school with Jews.'"
Scot Vorse, a longtime friend and ex-business partner of Bannon:
Vorse did not dispute Bannon's reputation as a hard-charging boss who demands success and performance from his employees, but said the criticism of him as a racist or anti-Semite is unwarranted.
"I know this guy. He's not perfect. But is he a racist, a sexist, an anti-Semitic? The answer is no. That's not the guy I know," Vorse told NBC News.
The Southern Poverty Law Center:
U.K.-based journalist Andre Walker:
The New York Observer columnist added that Bannon would be "superb" in his new position.