Mark Greaney is an American author known for his work in the thriller genre. He gained prominence for his collaboration with the late Tom Clancy, contributing to the Jack Ryan series. Greaney's writing often features intricate plots and well-researched details, appealing to fans of espionage and military fiction. In addition to his work with Clancy, Greaney has authored his own series, including the Gray Man novels, which follow a former CIA operative named Court Gentry. His books have been well-received, leading to adaptations in film and television, further expanding his audience.