Charlie Sheen has revealed he was diagnosed HIV positive some four years ago and has paid millions of dollars in blackmail to keep the information quiet.
Sheen, 50, told NBC's Today TV show he was speaking out because he was being blackmailed, and to refute tabloid reports that he has AIDS and was spreading it to other people.
"I have to put a stop to this onslaught, this barrage of attacks, of subtruths and very harmful and mercurial stories that are about me, that threaten the health of so many others that couldn't be further from the truth," he said.
"I am here to admit that I am in fact HIV positive," Sheen said, adding he was "not entirely sure" how he contracted the virus.
"It started with what I thought was a series of crushing headaches," he said. "I thought I had a brain tumor. I thought it was over."
Sheen said one of the reasons he disclosed the news about his health was to stop others from extorting him.
When he revealed his HIV status to friends "the truth became treason", leading to "blackmail and extortion and a circle of deceit".
"I trusted them, they were in my inner circle and thought they could be helpful. My trust turned to their treason," he said,
He acknowledged he had paid people "upwards of $10 million" in recent years for their silence about his condition but said he would no longer do so.
"I think I released myself from this prison today," he said.
Sheen's doctor, Robert Huizenga, also appeared on the "Today" show and said the actor "does not have AIDS."
Sheen, who is three times divorced, played the womanizing bachelor Charlie Harper on top-rated comedy series Two and A Half Men for eight years before being fired in 2011 for bad behavior that included cocaine-fueled partying with porn stars and a conviction for assaulting his ex-wife.
At the time, he was the highest paid actor on US television, with a reported salary of some $US1.8 million per episode.
Asked whether he had transmitted HIV to anyone since his diagnosis, Sheen said on Tuesday, "impossible." He said he had informed his ex-wives immediately after getting his diagnosis.
The actor said he had "always led with condoms and honesty when it came to my condition."
After being fired from Two and A Half Men, Sheen set up home with a number of porn stars he called "goddesses" and boasted on YouTube of having "tiger blood" in his veins.
Sheen, the son of West Wing TV actor Martin Sheen, said he doesn't feel any stigma from being HIV positive. HIV, or human immunodeficiency virus, weakens the immune system by destroying cells that fight disease and infection. No effective cure exists, but with proper medical care it can be controlled. If not, one can be infected with AIDS.
"I have a responsibility now to better myself and help a lot of other people ... Others may come forward and say 'thanks Charlie. Thanks for kicking the door open,'" he said.
Sheen also starred in 1980s movies Platoon and Wall Street, as well as the 2012-2014 cable TV comedy Anger Management, which was closely based on his life.
He has five children from his marriages to model Donna Peele, actresses Denise Richards and Brooke Mueller, and other relationships.
- Reuters / BBC