Monday, the 44th U.S. president stopped for a visit in Kenya, the home land of his father. There, Obama met with half-sister Auma Obama and Kenyan President Uhuru Kenyatta, who said he "had a refreshing chat" with the former U.S. leader.
The trip marks Obama's first to Africa since he left the White House in January 2017.
Obama will address the Nelson Mandela Foundation on Tuesday in what his aides call his most important public speech in the 18 months since he left the presidency.
"I was proud to visit sub-Saharan Africa more times than any other sitting President, and I'll return this week," Obama wrote in a Facebook post.
"In South Africa, the Obama Foundation will convene 200 extraordinary young leaders from across the continent and I'll deliver a speech to mark the 100th anniversary of Nelson Mandela's birth."
Mandela died in 2013 after a lifelong fight against apartheid and a 27-year imprisonment before he was elected South African leader. His birthday, July 18, is celebrated annually around the world as a remembrance of peace and reconciliation.
Obama spoke at Mandela's funeral, calling him "the last great liberator of the 20th century."
Other scheduled speakers at Tuesday's conference will include former President Bill Clinton, Nobel Peace Prize winner Archbishop Emeritus Desmond Tutu and Microsoft co-founder and philanthropist Bill Gates.
In his Facebook post, Obama shared a list of six books for "summer reading."