Harry, the younger son of King Charles, co-founded Sentebale in 2006 to help young people with HIV and AIDS in Lesotho and Botswana but resigned as a patron in March 2025 after a public falling-out with its chair of the board, Sophie Chandauka.
According to a record made public on Friday, Sentebale lodged a defamation claim in March at the High Court against Harry and one of his close friends, Mark Dyer, who was also a trustee of the charity.
The charity said it was seeking the court's "intervention, protection, and restitution" following an "adverse media campaign" conducted since last March that had "caused operational disruption and reputational harm to the charity, its leadership, and its strategic partners".
"The proceedings have been brought against Prince Harry and Mark Dyer, identified through evidence as the architects of that adverse media campaign, which has had significant viral impact and triggered an onslaught of cyber-bullying directed at the charity and its leadership," the charity's statement said.
A spokesperson for Harry, the Duke of Sussex, said he and Dyer "categorically reject these offensive and damaging claims".
"It is extraordinary that charitable funds are now being used to pursue legal action against the very people who built and supported the organisation for nearly two decades, rather than being directed to the communities the charity was created to serve," the spokesperson said in a statement.
Harry set up Sentebale, which means "forget-me-not" in the local language of Lesotho in Southern Africa, with Prince Seeiso of Lesotho nine years after Diana was killed in a Paris car crash.
Prince Seeiso and the then board of trustees also joined Harry in resigning from the charity when the dispute erupted.
During the public acrimony, Chandauka reported him and the trustees to Britain's charity regulator over alleged bullying and harassment.
Harry, 41, said what had occurred was "heartbreaking" and that "blatant lies hurt those who have invested decades" in supporting the children in Southern Africa.
After a review, the Charity Commission reported in August it had found no evidence of bullying, but said there had been weak governance and criticised all parties for allowing an internal dispute to become public.
