Theron, who is the UN’s Messenger of Peace, drew on her experience of growing up at the “terrifying early days” of the Aids crisis in South Africa to explain why she felt passionate about the topic.
“We saw the grim reality of death all around us,” she said, but added that things were better now with better treatment and prevention.
Millions more were, however, still at risk, especially young people and women.
“There is jeopardy,” she said.
“Young people are falling through the cracks in our fight against the epidemic.”
She said she hoped the epidemic could be ended if young people were empowered to take control of their health.
“I’ve seen what is possible when young people are empowered,” she said.
“I met young people who are happy to be alive today because there was a straight-talking adult who told them about how to stay safe. This is the beginning of the Aids-free generation we talk about.”