George Powers Cockcroft (born November 15, 1932), known by the pen name Luke Rhinehart, is an American novelist and screenwriter, author of eleven books. He is best known for his 1971 novel The Dice Man, the story of a psychiatrist who experiments with the multiple parts of his personality by making life decisions based on the roll of a die.

The Dice Man was critically and commercially well received. In 1995, the BBC called it "one of the fifty most influential books of the last half of the twentieth century," and in 1999 Loaded magazine named it "Novel of the Century". In 2013, the Telegraph listed it as one of the 50 great cult books of the last hundred years. Although first published in 1971, the book has enjoyed a 21st-century renaissance, being published or republished in more than 60 countries and translated into 27 languages.

Many of his subsequent books, within a variety of genres, have continued to explore both comic and philosophical ideas, following the precedent set by The Dice Man.