Combat Stress told the Daily Mail it had been involved in "filming for the series," which will see the Duke of Sussex visiting UK hospitals and treatment centres. Duchess Meghan is also rumoured to have been "involved with the production" in some way, the publication reports, but nothing has been confirmed or announced by Buckingham Palace or the Duke and Duchess of Sussex themselves yet.
Combat Stress describes itself as "the UK's leading charity for veterans' mental health." It has been providing support to former servicemembers dealing with issues such as post-traumatic stress disorder, depression and anxiety since 1919, according to its website. Prince Charles is its patron.
Harry, of course, is a veteran himself. He was deployed to Afghanistan twice – in 2007-2008 and 2012-2013 – with the Army Air Corps, and left the UK military in 2015. The duke has long been a supporter of veterans, and launched the Invictus Games for wounded and injured ex-servicemembers and veterans in 2014. He is also the current Captain General of the Royal Marines, though he will stand down from that post later this year as part of his stepping back from senior royal duties with the Duchess of Sussex. It's thought Princess Anne will take over that role.
The prince has also been outspoken about his own mental health, having revealed the difficulties he went through as a result of the death of his mother, Princess Diana, when he was just 12 years old.
"I can safely say that losing my mom at the age of 12 and therefore shutting down all of my emotions for the last 20 years has had quite a serious effect on not only my personal life, but also my work as well," he said on The Daily Telegraph's Mad World podcast in 2017. "I know there's huge merit in talking about your issues.
"Keeping it quiet will only ever make it worse, not just for you, but everyone else around you because you become a problem."
Harry, 32 at the time, then went on to say his failure to address his feelings caused him two years of "total chaos" in his 20s, leading him to seek professional help when he was 28 – partly due to the "huge support" he received from Prince William, his brother.
Last year, he told the same podcast he hopes his series with Oprah will help save lives and encouraged viewers to get help.
"When I did your podcast two years ago, the response made me realize what an impact sharing my story could have, and what an impact other stories can have for so many who are suffering silently," said Harry, who is now 35.
"If the viewers can relate to the pain and perhaps the experience, then it could save lives, as we will focus on prevention and positive outcomes."
Harry and Oprah's as-yet-untitled series will debut later this year.