South African actress Charlize Theron. Picture: Reuters

Thousands of people descended on Wanderers Stadium in Johannesburg on Tuesday to hear former US president Barack Obama deliver a speech at the 2018 Nelson Mandela Annual Lecture.

The lecture, organised by The Nelson Mandela Foundation and the Motsepe Foundation, is part of the centenary celebration of Nelson Mandela's birth. 

For nearly a decade, Mandela Day has been celebrated globally on 18 July in recognition of the late former president, who spent 67 years of his life in the service of humanity.

Among the some 15 000 people in attendance at the stadium was Oscar-winning actress Charlize Theron. 

A "star struck" fan shared a snap of him and the Benoni-born star on Twitter.

Other local stars who were also spotted at the stadium include "Isidingo" actors Aubrey Poo and Robert Whitehead, and TV personality Thapelo Mokoena.