Trump also named Keith Kellogg, a retired US Army General who has been serving as the acting national security adviser, as chief of staff to the National Security Council. Speaking to reporters in West Palm Beach where he spent the weekend, Trump said John Bolton, a former US ambassador to the United Nations, would serve the administration in another capacity.
McMaster is a highly regarded military tactician and strategic thinker, but his selection surprised some observers who wondered how McMaster, who is known for questioning authority, would deal with a White House that has not welcomed criticism.
He replaces a Trump loyalist. Michael Flynn, a retired Army lieutenant general, was fired as national security adviser on February 13 after reports emerged that he had misled Vice President Mike Pence about speaking to Russia's ambassador about US sanctions before Trump's inauguration.
The ouster, coming so early in Trump's administration, was another upset for a White House that has been hit by miscues, including the controversial rollout of a travel ban on people from seven Muslim-majority countries, since the Republican president took office on January 20.
Trump spent the weekend considering his options for replacing Flynn. His first choice, retired Vice Admiral Robert Harward, turned down the job last week.
The national security adviser is an independent aide to the president and does not require confirmation by the US Senate. The role has varied from administration to administration, but the adviser attends National Security Council meetings along with the heads of the State Department, the Department of Defense and key security agencies.
McMaster, 54, is a West Point graduate known as "H.R.," with a PhD in U.S. history from the University of North Carolina at Chapel Hill. He was listed as one of Time magazine's 100 most influential people in 2014, partly because of his willingness to buck the system.
A combat veteran, he gained renown in the first Gulf War - and was awarded a Silver Star - after he commanded a small troop of the US 2nd Army Cavalry Regiment that destroyed a much larger Iraqi Republican Guard force in 1991 in a place called 73 Easting, for its map coordinates, in what many consider the biggest tank battle since World War Two.
As one fellow officer put it, referring to Trump's inner circle of aides and speaking on condition of anonymity, the Trump White House "has its own Republican Guard, which may be harder for him to deal with than the Iraqis were". The Iraqi Republican Guard was ousted dictator Saddam Hussein's elite military force.
McMaster's fame grew after his 1997 book "Dereliction of Duty" criticized the country's military and political leadership for poor leadership during the Vietnam War.
