Writer and activist Kate Millett has died aged 82 while visiting Paris.
Her bestselling 1970 book Sexual Politics was seen as groundbreaking for taking on gender roles and the patriarchy.
Her death, from a heart attack, was confirmed to the Associated Press by a close contact and her publishing house.
She was seen as an icon of feminism's so-called "second wave". Her most famous book had a huge academic and popular influence.
Millett is thought to have been in France celebrating the birthday of her wife, photojournalist Sophie Keir.
'Bible of Women's Liberation'
Sexual Politics was based on Millett's 1969 PhD thesis from New York's Columbia University and made waves soon after being picked up by a publisher.
In a 1970 review, the New York Times called it "the Bible of Women's Liberation".
In the same year, the title - alongside an artist's portrait of the author - became a Time magazine cover.
The book is often filed with other classics of the era, including Betty Friedan's The Feminine Mystique (1963) and Germaine Greer's The Female Eunuch (1970).
Millett was a renowned feminist activist. She also campaigned for the Equal Rights Amendment in the US, for rights to abortions, and for women's rights in Iran, among other things.
In 1981, she collaborated with Ms Keir to write Going to Iran, which told of their joint trip to the country in 1979, during the Iranian revolution.
The pair had been arrested during the visit after attending women's protests in Tehran, and Millett later told People magazine of the fear she felt, especially as she overheard the authorities talking about her lesbianism, which she had written about openly.
However, she said she was most concerned for the Iranian women she left behind. "They can't get on a plane. That's why international sisterhood is so important," she said.
Life on a Christmas tree farm
Her other titles included The Prostitution Papers (1971) and The Politics of Cruelty (1994), an investigation of the use of torture across the world.
She later wrote about her struggles with depression.
Her first marriage was to Japanese sculptor Fumio Yoshimura, and she dedicated Sexual Politics to him. They divorced in 1985.
She married Ms Keir recently, according to the New York Times.
In later life, she spoke to the Guardian about making a living selling Christmas trees from her farm in upstate New York.
In the same interview, she said of her life in activism: "I love making trouble. It's a wonderful job. You don't get paid but you have a lot of adventures."