Former US president Barack Obama is expected to deliver the annual Nelson Mandela lecture in Johannesburg on Tuesday.

Around 9 000 people are expected to attend the event at Wanderers Stadium.

The lecture, in partnership with the Motsepe Foundation, comes a day before Nelson Mandela International Day and is themed: "Renewing the Mandela Legacy and Promoting Active Citizenship in a Changing World".

The Nelson Mandela Foundation said on its website that the lecture would focus on "creating conditions for bridging divides, working across ideological lines, and resisting oppression and inequality".

When announcing Obama as this year's speaker in April, foundation chief executive Sello Hatang explained: "We thought to ourselves: 'Who can best represent the legacy of Madiba? Who took the baton when he became president of his own country? Who would be able to deal with issues of democracy in a world ripped apart by corruption?'...We needed an African person."

President Cyril Ramaphosa would have a courtesy call with Obama at 13:00 ahead of his lecture delivery.

Ramaphosa will also be attending the lecture at 14:00 and a centenary dinner at Nasrec Expo Centre at 19:00.