In a YouTube video released on Monday, the British Olympian, 19, says, "come spring this year, my life changed massively when I met someone and it made me feel so happy, so safe ... That someone is a guy."
Daley says in the five-minute clip that he wanted "to put an end to all the rumors and speculation, and just say it, tell you guys," adding "is it a big deal? I don't think so."
"Of course I still fancy girls, but right now, I'm dating a guy, and I couldn't be happier," he said.
According to the Telegraph, Daley decided to make his announcement public after the Daily Mirror misquoted him as being "not gay."
Daley won the 10-meter platform gold at the 2009 world championships when he was 15. He took bronze in the same event at last year's London Olympics.