Mark Greaney is an American author born in Memphis, Tennessee in 1967. He is best known for his Gray Man series, a collection of action thriller novels centered on Court Gentry, a highly skilled assassin and CIA operative. Beyond his original work, Greaney has played a significant role in extending Tom Clancy's literary legacy. He co-authored Tom Clancy's final works and continued writing in the Ryanverse, the shared universe of Clancy's espionage and military fiction, from Clancy's death in 2013 through 2017.