Leonard B. Boudin (July 20, 1912 – November 24, 1989) was an American civil liberties attorney and left-wing activist who represented Daniel Ellsberg of Pentagon Papers fame and Dr. Benjamin Spock, the author of Baby and Child Care, who advocated draft resistance during the Vietnam War. Other opponents of the Vietnam war whom he represented were Julian Bond, William Sloan Coffin, and Philip Berrigan.
Boudin was the son of Clara (Hessner) and Joseph Boudin, Jewish immigrants.
He represented other controversial clients including the Church of Scientology, Judith Coplon, Jimmy Hoffa, the post-revolutionary government of Cuba, Paul Robeson, and others (such as persons subpoenaed by the House Un-American Activities Committee) thought or known to have Marxist views or Communist affiliations. Boudin was counsel to the National Emergency Civil Liberties Committee and a member of the National Lawyers Guild. He was the law partner of Victor Rabinowitz, himself counsel to numerous left-wing organizations and individuals.
Boudin argued and won unanimously the first case in which the United States Supreme Court invalidated a federal statute under the Free Speech Clause of the First Amendment, Lamont v. Postmaster General. He also argued and won the landmark case Kennedy v. Mendoza-Martinez, in which the Supreme Court held that draft dodgers could not be stripped of their citizenship without being criminally prosecuted and afforded the protections promised to criminal defendants in the Fifth and Sixth Amendments.