The Duke of Sussex has warned that most people "carry some form of unresolved trauma, loss or grief" as he launched his new Apple TV mental health series with Oprah Winfrey.
It has been revealed that the duke, 36, will open up about his own mental health struggles during the five-part series, which is called The Me You Can't See.
Beginning on May 21, it will feature interviews with celebrities including Lady Gaga and Glenn Close that "help lift the veil" on mental health and emotional wellbeing.
The series has been co-created and executive produced by Winfrey and the duke, who will each discuss their own experiences.
The duke said: "We are born into different lives, brought up in different environments, and as a result are exposed to different experiences. But our shared experience is that we are all human.
"The majority of us carry some form of unresolved trauma, loss, or grief, which feels - and is - very personal.
"Yet the last year has shown us that we are all in this together, and my hope is that this series will show there is power in vulnerability, connection in empathy, and strength in honesty."
Apple said the series "transcends culture, age, gender, and socioeconomic status to destigmatise a highly misunderstood subject and give hope to viewers who learn that they are not alone".
Other participants include Zak Williams, the son of late actor Robin Williams, US Olympic Boxer Virginia "Ginny" Fuchs, American basketball players DeMar DeRozan from the San Antonio Spurs and Langston Galloway from the Phoenix Suns and California-based chef Rashad Armstead.
The producers worked with 14 international experts and organisations to help shed light on the various methods of treatment.
Winfrey, who interviewed the Duke and Duchess of Sussex in March, said: "Now more than ever, there is an immediate need to replace the shame surrounding mental health with wisdom, compassion, and honesty."
The series was originally announced on the now defunct SussexRoyal Instagram page in 2019, before the couple quit as working royals and moved to the US.
Kensington Palace said at the time that it was intended to inspire viewers to have "an honest conversation about the challenges each of us faces", and how to equip ourselves with the "tools to thrive, rather than to simply survive" - a phrase the Duchess of Sussex has often used.
It had been due to be broadcast in 2020 but was delayed due to the pandemic.
The duke has previously spoken about the struggles he has faced since the 1997 death of his mother, Diana, Princess of Wales, and has made mental health one of the key focuses of his work.
In 2017, he revealed he had not sought counselling for more than two decades after losing his mother, eventually doing so after enduring two years of "total chaos" while still struggling in his late 20s to come to terms with his loss.
In March, he drew on his own experiences of grief to write the foreword for a children's book, created for young people who had lost loved ones over the last year.
The duke, who was 12 when his mother died in a Paris car crash, described how her death had left a "huge hole" inside him but highlighted the importance of seeking professional help.
"I will make a promise to you – you will feel better and stronger once you are ready to talk about how it makes you feel," he wrote.
The duke also spoke about his mother during his recent interview with Winfrey, revealing that he had "felt her presence" throughout the process of stepping back from royal life.
In 2019, the duke said of the new mental health series: "Our hope is that this series will be positive, enlightening and inclusive – sharing global stories of unparalleled human spirit fighting back from the darkest places, and the opportunity for us to understand ourselves and those around us better.
"I am incredibly proud to be working alongside Oprah on this vital series which we have been developing together for several months."