The US President announced on Twitter that John Bolton will take over from HR McMaster on April 9.
Washington is divided about most things, but on this the pundit class is unanimous: diplomat-turned-provocateur John Bolton's rise means more unapologetic, unilateral US action.
The 69-year-old Republican has been praised by conservatives as a straight-talking foreign policy hawk, while his critics label him as unhinged, dangerous and as one US television host memorably put it "a massive neocon on steroids".
Bolton and Trump disagree on Iraq war
As a key architect of the war against Iraq, John Bolton is somewhat of a surprising choice for President Donald Trump, who says he opposed that war.
Mr Bolton is accused of distorting intelligence reports to build the case that Saddam Hussein had weapons of mass destruction, which turned out to be wrong.
Unlike others involved in propelling the wars in Iraq and Afghanistan who have gone silent or publicly changed their mind, Mr Bolton remains outspoken and unapologetic.
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Bolton sees role as 'honest broker'
He's consistently argued for an uncompromising US stance backed by overwhelming force in crisis after crisis in the 12 years since he left office.
Are Iran and North Korea next?
Most recently, Mr Bolton has advocated preemptive strikes against North Korea and repeatedly suggested military interviention against Iran.
In 2007, he was already sick of diplomatic efforts on Iran declaring that: "The only thing that will stop Iran from getting nuclear weapons is regime change in Tehran."
It's these views that make him an attractive choice in the US President's mind, plus his disdain for the foreign policy establishment.
Mr Bolton has previously served as the United States ambassador to the United Nations - nominated by George W Bush in 2005.
He was chosen despite being a strong critic of the UN.
He once said that: "If the UN Secretariat building in New York lost 10 stories, it wouldn't make a lot of difference."
With views like that, it's no surprise he struggled to gain political support to continue in the role and stepped down at the end of 2006.
Never far from the spotlight
In the 12 years since, Mr Bolton has remained active in conservative foreign policy circles.
John Bolton was a foreign policy adivisor to former presidential candidate Mitt Romney. Source: AAP
The 69-year-old is currently a senior fellow at the American Enterprise Institute and has been an advisor to several conservative think tanks and lobby groups, including the National Rifle Association and Jewish Institute for National Security of America.
He also has ties to far-right, anti-Muslim bloggers Pamela Geller and Robert Spencer, writing the forward to their 2010 book The Post-American Presidency: The Obama Administration's War on America.
He's regularly shared his views as a commentator on Fox News and former presidential candidate Mitt Romney also engaged his services as a foreign policy adviser when he ran in 2012.
Mr Trump has reportedly long been keen to recruit the hawkish Bolton, but recently ousted Secretary of State Rex Tillerson was reluctant to work with him.
US media also reported at the time, that the President considered Mr Bolton's signature walrus moustache a negative.
While Mr Bolton hasn't shaved, Mr Tillerson's exit has cleared the path for Mr Bolton to return to the White House.
Aside from his political involvement, Mr Bolton has worked at several law firms and was a partner at the firm Lerner, Reed, Bolton and McManus.
With AFP.
