Irwin Shaw (born Irwin Gilbert Shamforoff, February 27, 1913 – May 16, 1984) was a prolific American playwright, screenwriter, novelist, and short-story author. His written works have sold more than 14 million copies.

He is best known for two of his novels: The Young Lions (1948), which explores the fate of three soldiers during World War II and was adapted into a film starring Marlon Brando and Montgomery Clift, and Rich Man, Poor Man (1970), which follows the lives of two brothers and a sister in the post-World War II era. In 1976, this novel was also adapted into a popular miniseries starring Peter Strauss, Nick Nolte, and Susan Blakely.

Shaw was born in the South Bronx, New York City, to Russian Jewish immigrants. His parents were Rose and Will Shamforoff. Shortly after his birth, his family moved to Brooklyn. He graduated from Brooklyn College with a Bachelor of Arts degree in 1934. Shaw began his screenwriting career in 1935 at the age of 21. His younger brother, David Shaw, became a noted Hollywood producer.