Waldo Miller Salt (October 18, 1914 – March 7, 1987) was an American screenwriter who was blacklisted by the Hollywood movie studio bosses during the era of McCarthyism.
Salt was born in Chicago, Illinois, the son of Winifred (née Porter) and William Haslem Salt, an artist and business executive. He graduated from Stanford University at age eighteen. The first of his nineteen films he wrote or in which he participated in the writing, was released in 1937 with the title The Bride Wore Red. He joined the American Communist Party in 1938, and was a civilian consultant to the U.S. Office of War Information during World War II.
Salt's career in Hollywood was interrupted when he was blacklisted after refusing to testify before the House Committee on Un-American Activities in 1951. Like many other blacklisted writers, while he was unable to work in Hollywood Salt wrote pseudonymously for the British television series The Adventures of Robin Hood. After the collapse of the blacklist, Salt won Academy Awards for Midnight Cowboy and Coming Home, and a nomination for his work on Serpico.