He fell ill on Friday while meeting US Secretary of State Hillary Clinton.
He was President Barack Obama's special envoy to Afghanistan and Pakistan. The presidents of both nations paid tribute to him.
Mr Obama called the 69-year-old, who was known for bringing warring leaders to the negotiating table, a "true giant of American foreign policy".
Mr Obama called the 69-year-old, who was known for bringing warring leaders to the negotiating table, a "true giant of American foreign policy".
Mr Holbrooke was meeting Ms Clinton at the US state department on Friday morning when he collapsed.
He was rushed to the US capital's George Washington University Hospital, where he underwent surgery to repair a tear in his aorta - the largest artery in the human body, which carries oxygenated blood from the heart.
He was rushed to the US capital's George Washington University Hospital, where he underwent surgery to repair a tear in his aorta - the largest artery in the human body, which carries oxygenated blood from the heart.
Mr Holbrooke's death comes as the Obama administration prepares to make public its latest review of US policy in Afghanistan and Pakistan later this week.
'Foreign policy giant'
Following the news of his death, Mr Obama said: "Michelle and I are deeply saddened by the passing of Richard Holbrooke, a true giant of American foreign policy who has made America stronger, safer and more respected.
"He was a truly unique figure who will be remembered for his tireless diplomacy, love of country, and pursuit of peace."
Ms Clinton also paid tribute to Mr Holbrooke's service, saying the US had lost "one of its fiercest champions and most dedicated public servants".
Following the news of his death, Mr Obama said: "Michelle and I are deeply saddened by the passing of Richard Holbrooke, a true giant of American foreign policy who has made America stronger, safer and more respected.
"He was a truly unique figure who will be remembered for his tireless diplomacy, love of country, and pursuit of peace."
Ms Clinton also paid tribute to Mr Holbrooke's service, saying the US had lost "one of its fiercest champions and most dedicated public servants".
"He was one of a kind - a true statesman - and that makes his passing all the more painful," she said in a statement.
Beginning with a foreign service posting in Vietnam in 1962, the veteran diplomat served under every Democratic president from John F Kennedy to Mr Obama.
Beginning with a foreign service posting in Vietnam in 1962, the veteran diplomat served under every Democratic president from John F Kennedy to Mr Obama.
But it was his role in Europe, helping bring to an end the war in Bosnia, that solidified his reputation as an important figure in foreign policy.
Nicknamed "the Bulldozer", the veteran diplomat once said he had no qualms about "negotiating with people who do immoral things", if it served efforts for peace.
Nicknamed "the Bulldozer", the veteran diplomat once said he had no qualms about "negotiating with people who do immoral things", if it served efforts for peace.
"He's a bulldog for the globe," United Nations Foundation president Tim Wirth once said.
Mr Holbrooke was named by Mr Obama as his special representative to Afghanistan and Pakistan shortly after the president took office in January 2009.
Mr Holbrooke was named by Mr Obama as his special representative to Afghanistan and Pakistan shortly after the president took office in January 2009.
Source : BBC News
