The Duke was photographed for Attitude after inviting LGBT+ people to Kensington Palace to hear their experiences of bullying.
Prince William has become the first member of the Royal Family to be photographed for the cover of a gay magazine.
The Duke invited Attitude to bring members of the LGBT+ community to Kensington Palace last month.He wanted to hear their experiences of bullying, and the affect it can have on mental health.
William revealed he would be appearing in Attitude after he and Kate signed a book of condolence for the victims of the Florida night club attack.
Forty nine people were killed at the Pulse gay club in Orlando on Sunday morning.
He told the magazine: "No one should be bullied for their sexuality or any other reason and no one should have to put up with the kind of hate that these young people have endured in their lives.
"The young gay, lesbian and transgender individuals I met through Attitude are truly brave to speak out and to give hope to people who are going through terrible bullying right now.
"Their sense of strength and optimism should give us all encouragement to stand up to bullying wherever we see it."
Last year, the PACE RARE report found that 33.9% of young LGB people had made at least one suicide attempt compared to 17.9% of young straight people.
The Prince added: "What I would say to any young person reading this who's being bullied for their sexuality: don't put up with it - speak to a trusted adult, a friend, a teacher, Childline, Diana Award or some other service and get the help you need.
"You should be proud of the person you are and you have nothing to be ashamed of."
Attitude's editor Matthew Todd said: "During my time as editor of Attitude I have met parents whose child has taken or lost their life after being bullied for being LGBT+ or even just perceived to be LGBT.
"I am very happy that the future King of the United Kingdom agrees this must stop."
A Kensington Palace spokesman said: "He (Prince William) has established a taskforce on the prevention of cyberbullying and, along with The Duchess of Cambridge and Prince Harry, is leading the Heads Together campaign on mental health and well-being.
"He knows that LGBT young people suffer unacceptably high rates of bullying and he was grateful to Attitude for facilitating such a serious conversation on this topic.
"He was moved by the stories he heard and impressed by the positivity and courage of the people he met."
Sky News.
