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 last month 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.
Harry's spokesperson did not immediately respond to a request for comment.
The charity's co-founder Prince Seeiso of Lesotho and the then-board of trustees also joined Harry in leaving Sentebale, which he helped set up nine years after Diana was killed in a Paris car crash and which means "forget-me-not" in the local language of Lesotho.
During the public acrimony last year, Chandauka reported him and the trustees to the United Kingdom's charity regulator over alleged bullying and harassment.
The 41-year-old prince said what had occurred was "heartbreaking" and that "blatant lies hurt those who have invested decades" in supporting the children in South 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.
