Richard Allen Posner (/ˈpoʊznər/; born January 11, 1939) is an American legal scholar and retired United States circuit judge who served on the U.S. Court of Appeals for the Seventh Circuit from 1981 to 2017. A senior lecturer at the University of Chicago Law School, Posner was identified in The Journal of Legal Studies as the most-cited legal scholar of the 20th century. As of 2021, he is also the most-cited American legal scholar of all time. He is widely considered to be one of the most influential legal scholars in the United States.
Posner is known for his scholarly range and for writing on topics outside of law. In his various writings and books, he has addressed animal rights, feminism, drug prohibition, same-sex marriage, Keynesian economics, law and literature, and academic moral philosophy, among other subjects.