Cindra Ladd, a philanthropist and former entertainment executive who is married to former Fox and MGM/UA chief Alan Ladd Jr., wrote in an op-ed piece published in the Huffington Post on Monday morning that the comedian drugged her and had sex with her when she was 21.
Ladd said she met Cosby in New York in 1969 while working for the late film producer Ray Stark.
"He was a 32-year-old internationally known comedian and television star, one of the most likable and popular entertainers in the business. He asked for my number and I gave it to him," she wrote.
She said they hung out, went to a movie, watched TV and ate pizza and hot dogs in her apartment with her roommate. Married to his wife Camille, Cosby was the "perfect gentleman," Ladd wrote.
On their way to a movie one night, Ladd wrote that she met Cosby at an apartment belonging to a friend of his. When she told Cosby she had a terrible headache, she said he offered her a capsule. Each time she asked him what it was, she said he responded, "Don't you trust me?"
Ladd wrote that she took the capsule and said to this day she only has vague recollections of that night.
"What I do recall, vividly and clearly, is waking up the next morning nude in the bed of his friend's apartment and seeing Cosby wearing a white terrycloth bathrobe and acting as if there was nothing unusual," she wrote. "It was obvious to me that he had had sex with me. I was horrified, embarrassed and ashamed. There was a mirror above the bed, which shocked me further."
Ladd said it never occurred to her to go to the police. "It was a different time and 'date rape' was a concept that didn't exist," she said.
Her roommate was the only person she discussed the incident with, she wrote, until nine years ago when she told her husband after another woman went public and sued Cosby. Ladd said she considered coming forward then, but the case was eventually settled.
With multiple women now accusing the comedian of sexual allegations, Ladd decided it was the "right thing" for her to speak out.
"This is the first time I have chosen to speak out about that night. It is also the last time I intend to address it publicly," she wrote. "I have no plans to sue, I don't want or need money. I have no plans for a press conference or for doing any interviews."
Cosby, 77, and his attorneys did not respond immediately to ABC News' request for comment about the latest accusation.
The comedian has denied any wrongdoing ever since allegations first surfaced in 2004. More women came forward in late 2014, and John P. Schmitt, a lawyer for Cosby, said of the new allegations in a statement, "The fact that they are being repeated does not make them true."
Another Cosby lawyer, Martin D. Singer, added: "These brand new claims about alleged decades-old events are becoming increasingly ridiculous, and it is completely illogical that so many people would have said nothing, done nothing, and made no reports to law enforcement or asserted civil claims if they thought they had been assaulted over a span of so many years."
Cosby, himself, weighed in before his show in Melbourne, Florida, in November.
"I know people are tired of me not saying anything, but a guy doesn't have to answer to innuendos," he told Florida Today. "People should fact check. People shouldn't have to go through that and shouldn't answer to innuendos."