Morris Leopold Ernst was an American lawyer and co-founder of the American Civil Liberties Union.
He was born in Uniontown, Alabama on August 23, 1888, to a Czech-born father and German mother. His parents were Jewish. He lived in various locations around New York City from the age of 2. He attended the Horace Mann School and graduated from Williams College in Williamstown, Massachusetts in 1909. He was admitted to the bar in 1913 after studying law at night.