Here's a selection of confirmed attendees compiled by The Associated Press:
U.S. President Barack Obama and first lady Michelle Obama as well as former presidents George W. Bush, Bill Clinton and Jimmy Carter.
U.N. Secretary General Ban Ki-moon and his predecessor Kofi Annan.
British Prime Minister David Cameron.
French President Francois Hollande and his predecessor Nicolas Sarkozy.
German President Joachim Gauck.
Canadian Prime Minister Stephen Harper and three of his predecessors.
Spanish Prime Minister Mariano Rajoy and Prince Felipe.
Brazilian President Dilma Rousseff and three of her predecessors, including Luiz Inacio Lula da Silva.
Indian President Pranab Mukherjee.
Australian Prime Minister Tony Abbott.
The Netherlands' Foreign Minister Frans Timmermans and King Willem-Alexander.
Danish Prime Minister Helle Thorning-Schmidt.
Norwegian Prime Minister Erna Solberg and Crown Prince Haakon.
Czech Foreign Minister Jan Kohout.
European Commission President Jose Manuel Barroso.
European Union Council President Herman Van Rompuy.
Top Vatican official Cardinal Peter Turkson of Ghana.
Slovak Foreign Minister Miroslav Lajcak.
Haiti's Prime Minister Laurent Lamothe.
Nepal's Foreign Minister Madhav Prasad Ghimire.
Sri Lanka's President Mahinda Rajapaksa.
Bangladesh's President Abdul Hamid.
Former Finnish President Martti Ahtisaari and former Irish head of state Mary Robinson as part of the delegation of The Elders, a group of former statesmen which Mandela helped to launch.
British entrepreneur Richard Branson and singer Peter Gabriel, who brought the idea of The Elders to Mandela.