US President Barack Obama has named Denis McDonough, his deputy national security adviser, as his new chief of staff.
Mr McDonough, 43, is taking over the position from Jack Lew, Mr Obama's nominee for treasury secretary.
He has worked for the president since Mr Obama's time in the Senate.
In a statement at the White House, the president called Mr McDonough "one of my closest and most trusted advisers".
"Denis has played a key role in every major national security decision of my presidency: ending the war in Iraq, winding down the war in Afghanistan, and from our response to natural disasters around the world like Haiti and the tsunami in Japan, to the repeal of Don't Ask Don't Tell," he said.
Mr McDonough's other predecessors in the role were Rahm Emanuel, William Daly and Pete Rouse.
Mr McDonough was one of several people alongside Mr Obama in a White House photograph watching the raid against Osama Bin Laden.
Counter-terrorism adviser John Brennan will be replaced by Lisa Monaco, former head of the justice department's National Security Division. Mr Brennan has been nominated to be the new head of the CIA.
Mr Obama also bade farewell on Friday to his election campaign manager, David Plouffe.
"If it were not for him, we would not have been as effective a White House, and I probably wouldn't be here," the president said.
White House communications director Dan Pfeiffer is being promoted to the job of senior adviser.