She died this morning at New York-Presbyterian Hospital after a brief hospitalization, said the Hearst Corp., which published Cosmopolitan.
"It would be hard to overstate the importance to Hearst of her success with Cosmopolitan, or the value of the friendship many of us enjoyed with her," said Frank Bennack, the CEO of Hearst today. "Helen was one of the world's most recognized magazine editors and book authors, and a true pioneer for women in journalism -- and beyond."
Brown spent three decades at the helm of Cosmopolitan, the racy magazine that catered to women's sexuality. She was hired as its editor in 1965.
She said at the outset that her aim was to tell a reader ''how to get everything out of life -- the money, recognition, success, men, prestige, authority, dignity -- whatever she is looking at through the glass her nose is pressed against.''
Brown, the author of the 1962 book "Sex and the Single Girl," said she never painted men as the enemy, but viewed sex as a powerful weapon.
She, along with Betty Friedan and Gloria Steinem, represented the so-called "second wave" of feminism, the post-World War II voices that followed the suffragists of the early 20th century.
In 1959, she married David Brown, who went on to be the producer of such movies as "Jaws," "The Sting" and "Driving Miss Daisy." He died in 2010.
"I often wondered over the years how she considered herself -- what kind of role model," said Terry O'Neill, executive director of the National Organization.
"She clearly aimed her communication at women and in some measure there was empowerment: You can be in charge of your own destiny and your own orgasms," said O'Neill.
But then she undercut that with "you can't live life without a man and you have to please him sexually."
Brown was born a self-confessed "hillbilly" in the Ozarks in the tiny town of Green Forest, Ark. Her father died when she was 10 and her sister suffered from polio.
According to a 2009 biography written by Bowdoin professor Jennifer Scanlon, Brown liked to quote from Carson McCullers: "I must go home periodically to renew my sense of horror."
When she wrote "Sex and the Single Girl'' -- advice and stories about how single women should be able to enjoy their sexuality -- she was an advertising copywriter.
Three years later, she became editor of Cosmopolitan.
''It was a terrific magazine,'' she said in 1997, according to The Associated Press. ''I would want my legacy to be, 'She created something that helped people.' My reader, I always felt, was someone who needed to come into her own.''
The magazine highlighted big-bosomed women and devoted itself to discovering the orgasm. In the 1970s, it included centerfolds of male icons at the time, such as Burt Reynolds.
Some feminists were appalled and protested at the magazine offices.
"I think her impact was very mixed," said Stephanie Coontz, author of the 2011 Book, "A Strange Stirring:" The Feminine Mystique and American Women at the Dawn of the 1960s."
"She certainly considered herself a feminist in every sense of the word," said Coontz. "She was for women's reproductive choices. For her, getting a career was just a stop-gap to getting a husband."