Prince Harry and Sir Elton John have hosted a panel at the 21st International AIDS Conference in South Africa on Thursday.
Prince Harry spoke about the work done by world leaders, including his mother, to fight the disease.
"When my mother held the hand of a man dying of AIDS in East London Hospital, no one would have imagined that just over a quarter of a century later, treatment would exist that could see HIV-positive people live full, healthy, loving lives," he said.
However, he warned there was no room for complacency, and that it was "time for us to step and acknowledge that stigma and discrimination still act as the greatest barrier to us defeating the disease one and for all".
Sir Elton praised the Prince for his work, and said the younger generation was needed to change the world.
"I'll be perfectly honest with you, young people won't listen to me," he said.
"If we want HIV programmes to work for young people, we can't tell them what to do and what to think. Don't let us older generation lecture you. Make us listen to you."