Catharine Alice MacKinnon (born October 7, 1946) is an American radical feminist legal scholar, activist, and author. She is the Elizabeth A. Long Professor of Law at the University of Michigan Law School, where she has been tenured since 1990, and the James Barr Ames Visiting Professor of Law at Harvard Law School. From 2008 to 2012, she was the special gender adviser to the Prosecutor of the International Criminal Court.

As an expert on international law, constitutional law, political and legal theory, and jurisprudence, MacKinnon focuses on women's rights and sexual abuse and exploitation, including sexual harassment, rape, prostitution, sex trafficking and pornography. She was among the first to argue that pornography is a civil rights violation, and that sexual harassment in education and employment constitutes sex discrimination.

MacKinnon is the author of over a dozen books, including Sexual Harassment of Working Women (1979); Feminism Unmodified (1987), Toward a Feminist Theory of the State (1989); Only Words (1993); a casebook, Sex Equality (2001 and 2007); Women's Lives, Men's Laws (2005); and Butterfly Politics (2017).