Canadian actor Elliot Page, formerly known as Ellen, says he is transgender.
Page, who was nominated for an Oscar for his role in the movie Juno, said he was able to "finally love who I am".
"I want to share with you I am trans, my pronouns are he/they and my name is Elliot," he wrote on social media.
"I feel overwhelming gratitude for the incredible people who have supported me along this journey."
Page also highlighted his fear over the announcement and criticised "political leaders" for policies they endorse against the trans community, without specifying who he was referring to.
"Despite feeling profoundly happy right now and knowing how much privilege I carry, I am also scared," he wrote.
"I'm scared of the invasiveness, the hate, the 'jokes' and of violence.
"To the political leaders who work to criminalise trans health care and deny our right to exist, and to all of those with a massive platform who continue to spew hostility towards the trans community: you have blood on your hands."
Page's wife, choreographer and dancer Emma Portner, described him as a "gift" following the announcement.
"Trans, queer and non-binary people are a gift to this world," she wrote on Instagram.
"I also ask for patience [and] privacy but that you join me in the fervent support of trans life every single day.
"Elliot's existence is a gift in and of itself."
Page broke through in his native country in a film called Hard Candy.
He also played the role as Kitty Pryde in the X-Men series, and garnered award nominations for his role as a teen girl facing an unplanned pregnancy in indie hit Juno.
Recently, he has starred in the Netflix show The Umbrella Academy.
There has been plenty of support for Page since the announcement was made.
Nick Adams, the director of transgender media for advocacy group GLAAD, said Page would become an inspiration for many around the world.
"Elliot Page has given us fantastic characters on-screen, and has been an outspoken advocate for all LGBTQ people," Adams said.
"He will now be an inspiration to countless trans and non-binary people.
"All transgender people deserve the chance to be ourselves and to be accepted for who we are."
Netflix also praised Page on their official Twitter account, saying the company was "proud of our superhero".
