Annan spent two terms as the head of the world diplomacy body, stepping down in 2006.
The death of the former UN Scribe was confirmed on his verified twitter handle by his family.
The Kofi Annan Foundation said the former UN boss, who won the Nobel Peace Prize for humanitarian work, died on Saturday aged 80.
He died in Switzerland, after a brief illness, according to a tweet by the Foundation
“It is with immense sadness that the Annan family and the Kofi Annan Foundation announce that Kofi Annan, former Secretary General of the United Nations and Nobel Peace Laureate, passed away peacefully on Saturday 18th August after a short illness,” the Foundation tweeted.
The Ghanaian was the second African to head the UN after Egypian Boutrous Boutrous Ghali, who was in charge between January 1992 to December 1996.
His tenure as UN secretary-general coincided with the Iraq War and the HIV/Aids pandemic.
After serving for 10 years at UN, Annan served as the UN special envoy for Syria, leading efforts to find a peaceful solution to the conflict.
Kofi Annan described his greatest achievement as the Millennium Development Goals which – for the first time – set global targets on issues such as poverty and child mortality.
Annan was born in Kumasi Ghana on 8 April 1938. After studying at Kwame Nkrumah University, he went on to study economics at Macalester College, International Relations from the Graduate Institute Geneva and Management at MIT.
He joined the UN in 1962, working for the World Health Organisation’s Geneva office. He went on to work in several capacities at the UN Headquarters including serving as the Under-Secretary-General for peacekeeping between March 1992 and December 1996.
He was the first UN Secretary General to be appointed from within the organisation’s bureaucracy.
His first marriage was to Titi Alakija, from 1965 to 1983. After the marriage collapsed, he married Nane Maria Lagergren in 1984.
He is survived by his wife, Nane and three children, Kojo, Ama and Nina.