He is the public face of the Donald Trump administration and will be the direct link to the press at daily briefings from the podium in the White House's West Wing.
But in his inaugural press conference following US President Donald Trump's inauguration on Friday (Jan 20), Press Secretary and Communications Director Sean Spicer lashed out at the media for their "shameful and wrong" portrayal of the inauguration crowd.
He claimed the media had doctored photographs of the National Mall in Washington DC to make the crowd size appear smaller than it actually was.
In his terse maiden statement on Saturday, Spicer said spots for 720,000 people were full when Trump took his oath.
But he was swiftly lampooned with memes by netizens after declaring "this was the largest audience to ever witness an inauguration - period".
The media and netizens highlighted findings by the Washington subway system, which reported it had 193,000 riders by 11am on Friday, compared with 513,000 at that same time during the 2009 inauguration of former president Barack Obama.
Aerial photographs published by the media had shown the audience size was significantly smaller than the crowd size in 2009.
Read also: White House vows to fight the media "tooth and nail"
So who is Sean Spicer? Here are seven facts about the man who is now speaking on behalf of arguably the world's most powerful man.
1) He was Trump's chief strategist and spokesman during the election
Spicer was Trump's chief strategist and mouthpiece during the race to the polls. He had been communications director of the Republican National Committee since 2011 and its chief strategist since 2015 before his White House appointment.
On his website - seanspicer.com, he describes himself as "a seasoned communicator and strategist" with a "diverse and extensive background including senior positions on Capitol Hill and political campaigns, and the top ranks of the administration".
2) He has a testy relationship with the media
Like Trump, Spicer is known for being very combative in his dealings with much of the mainstream media. He has often taken on the press on social media, describing certain news organisations and individual journalists as "dishonest" for their reports on his party and Trump.
He is not afraid to engage in shouting matches, recently locking horns with CNN's Michael Smerconish in an interview about Russia's meddling in the presidential election.
He has bone to pick with the media which started during college days. Back then, he accused the school paper of being "malicious and intentional" when it misspelled his surname as "Sphincter", reported The Daily Mail.
3) He and his wife had once worked for President George W. Bush
Spicer had previously worked for the last Bush administration as an assistant United States trade representative for media and public affairs. Observers have highlighted the irony that a man who had helped to tout free trade for a previous president is now working for one who is renouncing free trade deals.
His wife, Rebecca Miller, was the associate director of communications for President Bush. She had held television positions and is currently senior vice-president of public affairs and communications for the National Beer Wholesalers Association.
4) He criticised Trump for comments on Mexicans and John McCain
After Trump called Mexican immigrants criminals and rapists in 2015, Spicer appeared on CNN and said: "As far as painting Mexican-Americans with that kind of brush, I think it's not helpful to the cause."
He also defended Senator McCain after Trump questioned his military history and status as a war hero when he was a prisoner of war.
Spicer, who was then the communications director for the Republican National Committee, issued a statement stating "there is no place in our party or our country for comments that disparage those who have served honourably".
5) He's a member of the Navy Reserve and has a master's degree in national security
Spicer joined the Navy Reserve in 1999 and currently holds the rank of Commander. In 2012 he received a master's degree in National Security and Strategic Studies from the Naval War College in Newport, reported The Washington Post
In his hometown of Norfolk, Virginia, Spicer serves as director of the Navy Public Affairs Center Atlantic Reserve Unit, according to Leadership Institute.
6) He is addicted to chewing gum
He told The Washington Post that he can finish "two and a half packs by noon". His favourite is Orbit cinnamon gum, which he swallows whole after chewing.
"I talked to my doctor about it, he said it's no problem," he told the Post.
7) He makes small children cry?
A journalist told The Washington Post how her child would burst into tears upon hearing his voice when picking up the phone.
Often on the receiving end of Spicer admonishments, she apparently said: "Sean Spicer is a curse word in our house."