Kofi Annan spent virtually his whole career as an administrator in the United Nations, rising to become its seventh secretary-general and first black African to hold the post.
His death in Switzerland at age 80 after a short, unspecified illness was announced by his foundation on Saturday.
Annan's aristocratic style, cool-tempered elegance and political savvy helped guide him to two terms as secretary-general - from January 1 1997, to December 31 2006.
In 2001 he and the UN were jointly awarded the Nobel Peace Prize for his work reforming the organisation and for fighting for human rights.
During his tenure, Annan presided over some of the worst failures and scandals at the world body, one of its most turbulent periods since its founding in 1945.
His enduring moral prestige remained largely undented, however, both through charisma and by virtue of having negotiated with most of the powers in the world.
When he departed from the UN, he left behind a global organisation far more aggressively engaged in peacekeeping and fighting poverty, setting the framework for the UN's 21st-century response to mass atrocities and its emphasis on human rights and development.
Even out of office, Annan never completely left the UN orbit. He returned in special roles, including as the UN-Arab League's special envoy to Syria in 2012.
Annan took on the top UN post six years after the collapse of the Soviet Union and presided during a decade when the world united against terrorism after the September 11 attacks, and then divided deeply over the US-led war against Iraq.
The US relationship tested him as a world diplomatic leader.
"I think that my darkest moment was the Iraq war, and the fact that we could not stop it," Annan said in a February 2013 interview with Time magazine.
The US did not have the support in the Security Council," Annan recalled in the videotaped interview posted on The Kofi Annan Foundation's website.
"So they decided to go without the council. But I think the council was right in not sanctioning the war," he said.
Much of Annan's second term was spent at odds with the US, the UN's biggest contributor, as he tried to lean on the nation to pay almost $US2 billion in arrears.
Kofi Atta Annan was born April 8, 1938, into an elite family in Kumasi, Ghana, the son of a provincial governor and grandson of two tribal chiefs.
He became fluent in English, French and several African languages, attending an elite boarding school and the University of Science and Technology in Kumasi before finishing his undergraduate work in economics in Minnesota in 1961.
From there he went to Geneva, where he began his graduate studies in international affairs and launched his UN career.
Annan married Titi Alakija, a Nigerian woman, in 1965, and they had a daughter, Ama, and a son, Kojo. He returned to the US in 1971 and earned a master's degree at the Massachusetts Institute of Technology's Sloan School of Management.
The couple separated during the 1970s and, while working in Geneva, Annan met his second wife, Swedish lawyer Nane Lagergren. They married in 1984.
Annan worked for the UN Economic Commission for Africa in Ethiopia, its emergency force in Egypt, and the office of the High Commissioner for Refugees in Geneva, before taking a series of senior posts at UN headquarters in New York.
Just before becoming secretary-general, Annan served as UN peacekeeping chief and as special envoy to the former Yugoslavia, where he oversaw a transition in Bosnia from UN protective forces to Nato-led troops.
The UN peacekeeping operation faced two of its greatest failures during his tenure: the Rwanda genocide in 1994, and the massacre in the Bosnian town of Srebrenica in July 1995.
In both cases, the UN had deployed troops under Annan's command, but they failed to save the lives of the civilians they were trying to protect.
After became secretary-general, he called for UN reports on those two debacles - and they were highly critical of his management.
As secretary-general, Annan forged his experiences into a doctrine called the Responsibility To Protect, that countries accepted - at least in principle - to head off genocide, crimes against humanity, ethnic cleansing and war crimes.
In 1999, he was deeply involved in the process by which East Timor gained independence from Indonesia, and started the Global Compact initiative that has grown into the world's largest effort to promote corporate social responsibility.
Annan was also chief architect of what became known as the Millennium Development Goals, and played a central role in creating the Global Fund to Fight Aids, Tuberculosis and Malaria and the UN's first counter-terrorism strategy.
In 2005 the UN was facing almost daily attacks over allegations about corruption in the UN oil-for-food program in Iraq, bribery by UN purchasing officials and widespread sex abuse by UN peacekeepers.
It emerged that Annan's son, Kojo, had not disclosed payments he received from his employer, which had a $US10 million-a-year contract to monitor humanitarian aid under the oil-for-food program. The company paid at least $300,000 to Kojo so he would not work for competitors after he left.
An independent report criticised the secretary-general for being too complacent, saying he should have done more to investigate matters even if he was not involved with the awarding of the contract.
In his memoir, Annan recognised the costs of taking on the world's top diplomatic job, joking that "SG," for secretary-general, also signified "scapegoat" around UN headquarters.
After leaving his high-profile role, Mr Annan did not let up. In 2007, his Geneva-based foundation was created. That year he helped broker peace in Kenya, where election violence had killed over 1000 people.
He also joined The Elders, an elite group of former leaders founded by Nelson Mandela, eventually succeeding Desmond Tutu as its chairman after a failed interlude trying to resolve Syria's rising civil war.
Australian Associated Press
