The author of 'The Scarlet Letter' is Nathaniel Hawthorne. He was an American novelist and short story writer born in Salem, Massachusetts in 1804. He is best known for his works exploring the dark side of Puritan New England, such as 'The Scarlet Letter' and 'The House of Seven Gables'. His writing style often featured moral allegories with a Puritanical and anti-transcendentalist perspective.