Roger Nash Baldwin (January 21, 1884 – August 26, 1981) was one of the founders of the American Civil Liberties Union (ACLU). He served as executive director of the ACLU until 1950.

Many of the ACLU's original landmark cases took place under his direction, including the Scopes Trial, the Sacco and Vanzetti murder trial, and its challenge to the ban on James Joyce's Ulysses. Baldwin was a well-known pacifist and author.