Annan, who was born in Ghana in 1938, served as the seventh UN Secretary-General, from 1997 to 2006, and was the first to rise from within the ranks of the United Nations staff.
He had also been a member, since 2007, of The Elders, a humanitarian group of a dozen leaders and activists of worldwide stature formed by Nelson Mandela. In 2013, Annan became its chairman.
The Kofi Annan Foundation confirmed his death with “immense sadness” in a statement posted on Twitter.
Annan passed away peacefully Saturday morning after a short illness, with his wife Nane and their three children by his side during his final days, the statement said.
The foundation paid tribute to Annan as a “global statesman and a deeply committed internationalist who fought throughout his life for a fairer, more peaceful world.”
“During his distinguished career and leadership of the United Nations, he was an ardent champion of peace, sustainable development, human rights and the rule of law.”
Annan was awarded the Nobel Peace Prize jointly with the United Nations in 2001 “for their work for a better organized and more peaceful world
Despite his many achievements, Annan’s record was not unblemished. He was head of the United Nations’ peacekeeping operations in 1994, when some 800,000 people were killed in the Rwanda genocide, and in 1995 when thousands of Muslim men and boys were massacred in Srebrenica.
Annan would later say that he should have done more to prevent what unfolded in Rwanda, and that events there and in Srebrenica had reshaped his global thinking.
As news of Annan’s death has spread, many are paying tribute to a man who became a global figure as head of the United Nations but was also known by those close to him for his warmth, style and charm.
Current UN Secretary-General António Guterres told CNN that Annan had been “an enormous source of inspiration” to him, adding that the late leader had been committed to his principles and values even if he had to pay a heavy price for them.
“He was not only a statesman, he was not only a leader, he was a warm person who would support his friends in difficult moments. He was a true colleague and a true friend,” he said.
US Ambassador to the UN Nikki Haley said Annan “worked tirelessly to unite us and never stopped fighting for the dignity of every person.”
“Kofi Annan devoted his life to making the world a more peaceful place through his compassion and dedication to service,” she added.
The UN Migration Agency tweeted: “Today we mourn the loss of a great man, a leader, and a visionary.”
UN human rights chief Zeid Ra’ad Al Hussein said he was “grief-stricken” over Annan’s death. “Kofi was humanity’s best example, the epitome, of human decency and grace,” he said. “In a world now filled with leaders who are anything but that, our loss, the world’s loss becomes even more painful.”
A statement from The Elders said its members were “shocked and deeply saddened” by his death. “Kofi was a strong and inspiring presence to us all, and The Elders would not be where it is today without his leadership,” said deputy chairman Gro Harlem Brundtland, adding that the group was resolved to continue to uphold Annan’s values and legacy.