America Ferrera was sexually assaulted aged nine years old.
The 33-year-old actress has recalled a horrific incident during her younger years and admits she "lived with the shame and guilt" and had to see perpetrator everyday afterwards "for years to come".
In a statement posted to Twitter, she wrote: "First time I can remember being sexually assaulted I was 9-years-old. I told no one and lived with the shame and guilt thinking all along that I, a 9-year-old child, was somehow responsible for the actions of a grown man. I had to see this man on a daily basis for years to come. He would smile at me and wave, and I would hurry past him, my blood running cold, my guts carrying the burden of what only he & I knew -- that he expected me to shut my mouth and smile back.
"Ladies, let's break the silence to the next generation of girls won't have to live with this b******t (sic)"
America simply captioned her post "me too", joining a social media campaign to encourage women to speak up about sexual harassment.
At first, America tweeted that she had also been a victim, writing: "Me too. #MeToo (sic)"
But five hours later she shared her experiences with the world by posting the statement.
Alyssa Milano launched the social media campaign to implore anyone who has ever been sexually harassed or assaulted to write the words "me too".
She tweeted: "If you've been sexually harassed or assaulted write 'me too' as a reply to this tweet."
Under her own post, a screenshot read: "Me too.
"Suggested by a friend: "If all the women who have been sexually harrassed or assaulted wrote 'Me too.' as a status, we might give people a sense of the magnitude of the problem.(sic)"
Several stars have responded to the campaign, including Lady Gaga, Gabrielle Union and Evan Rachel Wood.
Evan wrote: "Being raped once made it easier to be raped again. I instinctually shut down. My body remembered, so it protected me. I disappeared. #metoo
"Because I was shamed and considered a "party girl" I felt I deserved it. I shouldnt have been there, I shouldn't have been "bad" #metoo
"Now I know that no matter how much I partied, got wild, or inebriated myself, I never raped anyone. So that should never be an excuse #metoo (sic)"
Alyssa's decision to launch the campaign came shortly after she spoke out against Hollywood movie producer Harvey Weinstein, who has been accused of sexually harassing women for decades.
He has been sacked from his own Weinstein Company and his wife, fashion designer Georgina Chapman, has left him following the allegations.