Mark Greaney (born 1967) is an American novelist focusing on thrillers. He is best known as Tom Clancy's collaborator on his final books during his lifetime, and for continuing the Jack Ryan character and the Tom Clancy universe following Clancy's death in 2013. He is also known for the Gray Man series of novels, which was produced by Netflix into a feature film.

Born in Memphis, Tennessee, he is the son of Ed Greaney, a presence at WMC-TV Memphis for over 50 years and the namesake for the station's current newsroom. Greaney has degrees in political science and international relations, which would later play a major part in his writing career.