Richard Edgar "Rick" Castle is a fictional character on the ABC crime series Castle. He is portrayed by actor Nathan Fillion. The character, Richard Castle, is a famous mystery novelist who becomes involved in crime solving when he teams up with NYPD Detective Kate Beckett.

Richard Castle is also used as a pseudonym under which a set of real books about the characters Derrick Storm and Nikki Heat are published. These books, based on the novels mentioned in the television series, achieved significant success, becoming New York Times bestsellers. The series of books was actually written by screenwriter and author Tom Straw. Nathan Fillion appears as the face of Richard Castle on the books and official website and participates in book signings.