Obama, who like Mandela was his nation’s first Black president, has cited Mandela as his own inspiration for entering politics.
He said his death should prompt self-reflection.
“With honesty, regardless of our station or our circumstance, we must ask: How well have I applied his lessons in my own life?” Obama said.
“It is a question I ask myself, as a man and as a president. We know that like South Africa, the United States had to overcome centuries of racial subjugation. As was true here, it took sacrifice—the sacrifices of countless people, known and unknown—to see the dawn of a new day.”
The presidents of Namibia, India, Cuba and South Africa were also designated speakers, as were Roussef and Chinese Vice President Li Yuanchao.
“South Africa has lost a hero, they have lost a father. The world has lost a beloved friend and mentor,” United Nations Secretary-General Ban Ki-moon said to loud cheers. “Nelson Mandela was more than one of the greatest leaders of our time; he was one of the greatest teachers. And he taught by example.”
The stadium, which can seat around 90,000 people, was not full, and speeches were hard to hear at times. But the celebratory mood was evident as thousands clapped and waved South African flags throughout the service.
CNN’s Michael Pearson, Athena Jones, Holly Yan, Chris Cuomo, Kim Norgaard, Robin Curnow, Arwa Damon Errol Barnett and David McKenzie contributed to this report.