The celebrities are sharing their secrets as part of Sentebale’s #FeelNoShame campaign for World Aids Day.
A video of Prince Harry asking the public to join in and share their secrets on social media appeared on a microsite at midnight and he will release another video at 1pm today, revealing his own secret. People can also donate money to the charity through the website.
Throughout the day, other celebrities – including Gemma Arterton, Ricky Hatton and Ricky Tomlinson – will reveal secrets on the microsite too.
CHI & Partners worked with tech company Visual Voice to create the campaign, which aims to highlight the stigma and shame felt by HIV sufferers across the world.
The charity behind the campaign, Sentebale, was co-founded by Prince Harry and Prince Seeiso of Lesotho (a landlocked country within South Africa) in 2006.
The organisation provides food, medication and education to children in Lesotho, which has one of the highest incidences of HIV and Aids in the world.
Prince Harry said: "To show our support for the children of Lesotho [where Sentebale works], and help reduce the stigma for all those affected by HIV, we are turning this World Aids Day into a day in which no one should feel any shame about their secrets.
"Together, we can tackle the stigma surrounding HIV and give the young people carrying it the childhood they deserve. The childhood so many of us take for granted."
The work was created by Colin Smith and Angus Vine. Visual Voice was the social media and technology company on the campaign while M/SIX handled the media.
Jonathan Burley, the executive creative director at CHI & Partners, said: "#FeelNoShame is a powerful, simple vehicle for a very serious message – communication saves lives. HIV sufferers are dying simply because they’re too ashamed to speak up and seek support.
"With #FeelNoShame, we and the celebrities we are working with hope to spark a long-term shift in how people think about HIV/Aids in the developing world, rejecting the shame and stigma people misguidedly associate with the disease."