Katherine Murray Millett (September 14, 1934 – September 6, 2017) was an American feminist writer, educator, artist, and activist. She attended the University of Oxford and was the first American woman to be awarded a degree with first-class honors 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. The feminist, human rights, peace, civil rights, and anti-psychiatry movements were some of Millett's principal causes.