Zechariah Chafee, Jr. (born Dec. 7, 1885, Providence, R.I., U.S.—died Feb. 8, 1957, Boston, Mass.) was a U.S. legal scholar known for his advocacy of civil liberties. His first book, Freedom of Speech (1920), was evoked by measures aimed at political dissenters in World War I. A rewritten and expanded version, Free Speech in the United States (1941), became a leading text of U.S. libertarian thought.
From 1916 until he retired 40 years later, Chafee was a professor at the Harvard Law School, of which he was a graduate. He was an authority on equity, negotiable instruments, and unfair business competition.