The 19-year-old made the admission in a YouTube video to his fans, which he circulated on Twitter with the caption: "Got something I need to say...not been an easy decision to make, hope you can support me!"
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He began the five-and-a-half minute clip by saying: "Most of you are probably wondering why I'm doing this video. My life's been a bit of a rollercoaster to say the least."
He goes on to say: "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."
In the video information, Tom tells his fans: "I wanted you to hear this from me."
In the clip, he says of his feelings: "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 'Okay'.
"And my whole world changed there and then."
The Devon-born swimming champ adds: "Of course I still fancy girls but right now I'm dating a guy and I couldn't be happier."
The Twitterverse was flooded with messages of support from fans and celebrities alike. Una Foden, of girlband the Saturdays, wrote: "Huge respect for @tomdaley1994 for coming out in such a brave manner. Lovely guy too X"