Morris Leopold Ernst (August 23, 1888 – May 21, 1976) was an American lawyer and a prominent attorney for the American Civil Liberties Union (ACLU). In public life, he defended and asserted the rights of Americans to privacy and freedom from censorship, playing a significant role in challenging and overcoming the banning of certain works of literature, including James Joyce's Ulysses and Radclyffe Hall's The Well of Loneliness. He asserted the right of media employees to organize labor unions and promoted an anti-communist stance within the ACLU itself. Additionally, he was a member of the President's Committee on Civil Rights.