Katherine Murray Millett (September 14, 1934 – September 6, 2017) was an American feminist writer, educator, artist, and activist. She attended Oxford University and was the first American woman to be awarded a degree with first-class honours after studying at St Hilda's College, Oxford. She has been described as "a seminal influence on second-wave feminism", and is best known for her book Sexual Politics (1970), which was based on her doctoral dissertation at Columbia University. Journalist Liza Featherstone attributes the attainment of previously unimaginable "legal abortion, greater professional equality between the sexes, and a sexual freedom" in part to Millett's efforts.
Millett was a leading figure in second-wave feminism. She and Sidney Abbott, Phyllis Birkby, Alma Routsong, and Artemis March were among the members of CR One, the first lesbian-feminist consciousness-raising group, although Millett identified as bisexual by late 1970.
She contributed the piece "Sexual politics (in literature)" to the 1970 anthology Sisterhood Is Powerful: An Anthology of Writings from the Women's Liberation Movement, edited by Robin Morgan.
She became a spokesperson for the feminist movement following the success of the book Sexual Politics (1970), but struggled with conflicting perceptions of her as arrogant and elitist, and the expectations of others to speak for them, which she covered in her 1974 book, Flying.
Millett was one of the first writers to describe the modern concept of patriarchy as the society-wide subjugation of women.  Biographer Gayle Graham Yates said that "Millett articulated a theory of patriarchy and conceptualized the gender and sexual oppression of women in terms that demanded a sex role revolution with radical changes of personal and family lifestyles". Betty Friedan's focus, by comparison, was to improve leadership opportunities socially and politically and economic independence for women.
Millett wrote several books on women's lives from a feminist perspective. For instance, in the book The Basement: Meditations on a Human Sacrifice (1979), completed over four years, she chronicled the torture and murder of Indianapolis teenager Sylvia Likens by Gertrude Baniszewski in 1965 that had preoccupied her for 14 years. With a feminist perspective, she explored the story of the defenseless girl and the dynamics of the individuals involved in her sexual, physical and emotional abuse. Biographer Roberta M. Hooks wrote, "Quite apart from any feminist polemics, The Basement can stand alone as an intensely felt and movingly written study of the problems of cruelty and submission." Millett said of the motivation of the perpetrator: "It is the story of the suppression of women. Gertrude seems to have wanted to administer some terrible truthful justice to this girl: that this was what it was to be a woman".
Millett and Sophie Keir, a Canadian journalist, travelled to Tehran, Iran in 1979 for the Committee for Artistic and Intellectual Freedom to work for Iranian women's rights. Their trip followed actions taken by Ayatollah Khomeini's government to prevent girls from attending schools with boys, to require working women to wear veils, and not to allow women to divorce their husbands. Thousands of women attended a protest rally held at the University of Tehran on International Women's Day, March 8. About 20,000 women attended a march through the city's Azadi Square. Millett and Keir, who had attended the rallies and demonstrations, were removed from their hotel room and taken to a locked room in immigration headquarters two weeks after they arrived in Iran. They were threatened that they might be put in jail and, knowing that homosexuals were executed in Iran, Millett also feared she might be killed when she overheard officials say that she was a lesbian. After an overnight stay, the women were put on a plane that landed in Paris. Although Millett was relieved to have arrived safely in France, she was worried about the fate of Iranian women left behind, "They can't get on a plane. That's why international sisterhood is so important." She wrote about the experience in her 1981 book Going to Iran. Millett is featured in the feminist history film She's Beautiful When She's Angry (2014).