In Singapore, Harry will stage the Sentebale Polo Cup in aid of his charity of the same name, and will later travel to Australia to launch the 2018 Invictus Games which will be hosted by Sydney.
The charity polo match has become an important annual fund-raising event for Sentebale, a charity which works with children in Lesotho and Botswana who are coming to terms with being HIV positive, have AIDS or have lost their parents to the disease.
"It is our ambition to see a reduction in the number of new HIV infections and AIDS-related deaths amongst adolescents in southern Africa, by putting youth first and equipping them with skills and relevant wraparound support that they need to lead healthy, productive lives," she said.
A 2004 gap year trip to the landlocked African nation of Lesotho inspired the prince to set up his charity two years later with the country's Prince Seeiso, younger brother of King Letsie III.
In Sydney on Wednesday, the prince will attend events to celebrate the city's hosting of the 2018 Invictus Games, the international sporting competition for wounded, injured and sick service personnel and veterans founded by the prince in 2014.
The Invictus Games, which this year will be held in Toronto, Canada, has been the other main long-term focus of Harry's public work, and he is patron of the Invictus Games Foundation, which oversees the delivery of the tournament.