Helen Gurley Brown, the iconic editor in chief of fashion magazine Cosmopolitan whose frank, modern attitudes about women and sex brought her fans and simultaneously made her a lightning rod, died Monday after a brief hospitalization in New York, according to a press release issued by Hearst Corporation. She was 90.

With her landmark 1962 bestseller "Sex and the Single Girl" and her stewardship of "Cosmopolitan," from 1965 to 1997, she opened up conversations about sexuality at a time when female empowerment was a growing...