After Prince Harry bravely revealed his mental health struggles in an interview with the Daily Telegraph, his brother has spoken up alongside pop star Lady Gaga.
The unlikely duo teamed up to encourage people to "open up" about their mental health struggles and start a conversation about it, the Telegraph reports.
They were filming the video for mental health charity Heads Together, which was started by the Duke and Duchess of Cambridge as well as Prince Harry.
In the video, which was streamed on Facebook as Prince William spoke to the pop star, Lady Gaga said she felt people with mental health challenges were "not hiding anymore".
The Duke said: "It's time that everyone speaks up and really feels very normal about mental health, it's the same as physical health. Everybody has mental health and we shouldn't be ashamed of it and just having a conversation with a friend or family member can really make such a difference."
Lady Gaga said: "For me waking up every day feeling sad and going on stage is just very hard to describe.
"There's a lot of shame attached to mental illness, you feel like something's wrong with you. And in my life I go 'oh my goodness, look at all these beautiful and wonderful things that I have, and I should be so happy'.
"But you can't help it if in the morning when you wake up, you are so tired, you are so sad and you are so full of anxiety and the shakes that you can barely think.
"But it was like saying 'this is a part of me, and that's OK'."
William has called for the end of "stiff upper lip" culture, and said he wants a culture where his children, George and Charlotte, can speak about their emotions.
Saying the idea that successful, strong people do not suffer their own emotional difficulties is false, he added: "We all do. It's just few of us speak about it."
In an interview for CALMzine, the charity magazine aimed at tackling mental health in men, the Duke has now said: "Attitudes are changing and this is being helped by high-profile people talking about their experience.
"Men like Professor Green, Freddie Flintoff and Rio Ferdinand have led the way and made films for Heads Together showing the conversations they have had about pressures on their mental health.
"The recent interview by Stormzy about his depression was incredibly powerful and will help young men feel that it's a sign of strength to talk about and look after your mind as well as your body.
"There may be a time and a place for the 'stiff upper lip', but not at the expense of your health."