Olympic diver Tom Daley has revealed he is in a relationship with a man.
In a YouTube broadcast, the 19-year-old London 2012 bronze medallist said: "In spring this year my life changed massively when I met someone, and they make me feel so happy, so safe and everything just feels great.
"That someone is a guy."
Edward Lord, chairman of the Amateur Swimming Association, said: "To be one of the first British Olympic athletes to come out is very brave."
'Still fancy girls'
Daley, from Plymouth in Devon, said: "It did take me by surprise a little bit. It was always in the back of my head that something like that could happen.
"But it wasn't until spring this year that something just clicked. It felt right and I thought 'OK'.
"And my whole world changed there and then."
He added: "Of course I still fancy girls but right now I'm dating a guy and I couldn't be happier."
Mr Lord said: "We must all support Tom in taking this incredibly courageous step."
He said he hoped it would "be a signal not just to other sportspeople but to all young people that you can be open about your sexuality, even in a very public environment."
He added: "I am very proud of Tom".
Gay rights campaigners Stonewall tweeted: "Moving and inspiring video from @TomDaley1994. A role model for thousands of other young people."
Former England footballer Gary Lineker tweeted: "Delighted that @TomDaley1994 is happy in his new relationship. Well done for sharing it. Good luck to them both."
Daley's diving coach, Andy Banks, who was with the teenager during training in Plymouth on Monday, said it would not affect his performance.
He said: "Tom being Tom, it will be situation normal and he'll get on with the job. He's diving very well."
'Overwhelmed by support'
Daley said his father Rob, who died of cancer aged 40 in 2011, always said to him: "As long as you are happy, I'm happy."
He added: "My mum has been so supportive as well."
Daley said there had been "mixed opinions" from some friends and family when he told them that he was making the announcement.
"Lots of them did not believe it," he said.
"Lots of them wanted me to keep it quiet. I didn't want to get my words twisted.
"I wanted to put an end to all the rumours and speculation, and just say it and tell you guys. It's what I want to do.
"My friends and family are always there to support me and I hope you guys can be, too.
"I mean I'm still Tom, I still want to win an Olympic gold medal in Rio 2016 for Great Britain.
"I am still as motivated as ever to do that. It would be great to have you guys on that journey, too."
He later tweeted to his 2.5m followers: "Overwhelmed by all the support! Means the world! Thanks so much guys."