The Aubrey–Maturin series is a sequence of historical novels — 20 completed and one unfinished — by Patrick O'Brian, set during the Napoleonic Wars and centering on the friendship between Captain Jack Aubrey of the Royal Navy and his ship's surgeon Stephen Maturin, who is also a physician, natural philosopher, and secret agent. The 21st novel of the series, left unfinished by O'Brian's death in 2000, appeared in print in late 2004.