Bill Goldstein, a writer who was working on a biography of Kramer, confirmed the news to The Associated Press. Kramer’s husband, David Webster, told The New York Times that Kramer died of pneumonia on Wednesday.

Kramer, who wrote “The Normal Heart” and founded the AIDS Coalition to Unleash Power, or ACT UP, lost his lover to acquired immune deficiency syndrome in 1984 and was himself infected with the virus. He also suffered from hepatitis B and received a liver transplant in 2001 because the virus had caused liver failure.

He was nominated for an Academy Award for his screenplay for “Women in Love,” the 1969 adaptation of D.H. Lawrence’s novel. It starred Glenda Jackson, who won her first Oscar for her performance.

He also wrote the 1972 screenplay “Lost Horizon,” a novel, “Faggots,” and the plays “Sissies’ Scrapbook,” “The Furniture of Home,” “Just Say No” and “The Destiny of Me,” which was a finalist for the Pulitzer Prize in 1993.

But for many years he was best known for his public fight to secure medical treatment, acceptance and civil rights for people with AIDS. He loudly told everyone that the gay community was grappling with a plague.

In 1981, when AIDS had not yet acquired its name and only a few dozen people had been diagnosed with it, Kramer and a group of his friends in New York City founded Gay Men’s Health Crisis, one of the first groups in the country to address the epidemic.

He tried to rouse the gay community with speeches and articles such as “1,112 and Counting,” published in gay newspapers in 1983.

“Our continued existence as gay men upon the face of this earth is at stake,” he wrote. “Unless we fight for our lives, we shall die.”

The late journalist Randy Shilts, in his best selling account of the AIDS epidemic “And the Band Played On,” called that article “inarguably one of the most influential works of advocacy journalism of the decade” and credited it with “crystallizing the epidemic into a political movement for the gay community.”

Kramer lived to see gay marriage a reality and joined one such union himself in 2013 but never rested. “I’m married,” he told The AP. “But that’s only part of where we are. AIDS is still decimating us and we still don’t have protection under the law.”

Kramer split with GMHC in 1983 after other board members decided to concentrate on providing support services to people with AIDS. It remains one of the largest AIDS-service groups in the country.

After leaving GMHC, Kramer gave voice to his grief and frustration by writing “The Normal Heart,” in which a furious young writer — not unlike Kramer himself — battles politicians, society, the media and other gay leaders to bring attention to the crisis.

The play premiered at The Public Theater in April 1985. Associated Press drama critic Michael Kuchwara called it an “angry but compelling indictment of a society as well as a subculture for failing to respond adequately to the tragedy.”

A revival in 2011 was almost universally praised by critics and earned the best revival Tony. Two actors from it — Ellen Barkin and John Benjamin Hickey — also won Tonys. Joe Mantello played the main character of Ned Weeks, the alter ego of Kramer.

“I’m very moved that it moved so many people,” he said at the time. Kramer often stood outside the theater passing out fliers asking the world to take action against HIV/AIDS. “Please know that AIDS is a worldwide plague. Please know there is no cure,” it said.

The play was turned into a TV film for HBO in 2014 starring Mark Ruffalo, Jonathan Groff, Matt Bomer, Taylor Kitsch, Jim Parsons, Alfred Molina, Joe Mantello and Julia Roberts. It won the Emmy for best movie, and Kramer stood onstage in heavy winter clothing as the statuette was presented to director Ryan Murphy.

The 1992 play “The Destiny of Me,” continues the story of the character Weeks from “The Normal Heart.” Weeks, in the hospital for an experimental AIDS treatment, reflects on the past, particularly his relationship with his family. His parents and brother appear to act out what happened in the past, as does the young Ned, who confronts his older self.

In 1987, Kramer founded ACT UP, the militant group that became famous for staging civil disobedience at places like the Food and Drug Administration, the New York Stock Exchange and Burroughs-Wellcome Corp., the maker of the chief anti-AIDS drug, AZT.

ACT UP’s protests helped persuade the FDA to speed the approval of new drugs and Burroughs-Wellcome to lower its price for AZT.

Kramer soon relinquished a leadership role in ACT UP, and as support for AIDS research increased, he later found some common ground with health officials whom ACT UP had bitterly criticized. (At the Emmy Awards, Kramer wore an ACT UP baseball cap.)

“There are many people who feel that ACT UP hurt itself by so many of us going to work inside, with the very system that we were formed to protest against,” Kramer told The New York Times in 1997. “There’s good reason to believe that. On the other hand, when you are given the chance to be heard a little better, it’s hard to turn down.”

In 1997, he clashed with administrators at his alma mater, Yale University, when they turned down his multimillion-dollar offer to endow a professorship in gay studies.

He said such the field could consider gays’ contributions in history, sociology, politics and culture, as well as on aspects of sexual identity. The school said the field was too narrow for a permanent professorship and, besides, there was a hiring freeze.

“I have no question in my mind that they were rejected because of extreme homophobia,” Kramer responded. “There’s no question that Yale is not a friendly place for gay professors or teachers.”

Kramer said he wanted to help gay students feel more comfortable than he did when he was at Yale. In 1953, during his freshman year, he attempted suicide with pills. “I tried to kill myself because, as far as I was concerned, I was the only gay kid on the face of the earth,” he said.

Kramer never softened the urgency of his demands. He found time in 2011 to help the American Foundation for Equal Rights mount their play “8” on Broadway about the legal battle over same-sex marriage in California.

One of his last projects was the massive two-volume “The American People,” which chronicled the history of gay people in America. It took him decades to write.

“I just think it’s so important that we know our history — the history of how badly we’re treated and how hard we have to fight to get what we deserve, which is equality,” he told The AP.

At the 2013 Tonys, he was honored with the Isabelle Stevenson Award, which honors a member of the theater community for philanthropic or civic efforts.

A few months later, Kramer married his longtime partner, architect David Webster, in the intensive care unit of NYU Langone Medical Center, where Kramer has been recovering from surgery for a bowel obstruction. He had set up the wedding plans before his health emergency and wouldn’t let that stop him.

The moment was bittersweet: The legendary gay rights activist finally got to celebrate his union legally but was so sick that he couldn’t sign his name. He had planned to exchange vows on his balcony but was knocked into a stupor two days before the event.

“It certainly wasn’t the wedding present one wanted to share,” he said. Pointing to his head, he added: “I’m just grateful the old thing still works, because evidentially it didn’t for a while.”