Ricky Martin came out on his Twitter page, confirming what many had believed for years.
The Puerto Rican star wrote: "I am proud to say that I am a fortunate homosexual man. I am very blessed to be who I am."
Martin, 38, said his coming out marked "an amazing turning point in my life".
The decision was made a few months ago when he began writing his memoirs, he said.
"From the moment I wrote the first phrase I was sure the book was the tool that was going to help me free myself from things I was carrying within me for a long time," Martin wrote on his website.
He said the secret had become "too heavy for me to keep inside" and his sexuality was "something worth celebrating."
The star, who has twin sons by a surrogate mother, said he did not come out earlier because his advisers said the move would ruin his career.
In 2000, American TV journalist Barbara Walters questioned him about whether he was gay, but he refused to disclose it.
Gay rights groups said Martin would be an inspiration to millions of young people coming to terms with their sexuality.
Jarrett Barrios, the president of the US-based Gay and Lesbian Alliance Against Defamation, welcomed what he called Martin's "openness and honesty".
The Latin pop singer became a household name with songs such as the 1999 hit Livin' La Vida Loca and She Bangs.
(Story form Sky News)
