Patrick O'Brian (born Richard Patrick Russ) was an English novelist and translator, celebrated for his Aubrey–Maturin series. These sea novels are set in the Royal Navy during the Napoleonic Wars and focus on the friendship between the English naval captain Jack Aubrey and the Irish–Catalan physician Stephen Maturin. The series, comprising 20 novels, beginning with Master and Commander, is renowned for its meticulous depiction of early 19th-century life, alongside its authentic and evocative language. A partially finished 21st novel was published posthumously with both handwriting and typescript pages.

O'Brian penned various other novels and short stories prior to the success of the Aubrey–Maturin series. Additionally, he was a translator of French works into English and authored biographies of Joseph Banks and Pablo Picasso.

His significant literary success arose later in life when the series was picked up by an American publisher, gaining acclaim while the author was in his seventies. Toward the end of his life, the British media revealed details about his early life and name change post-war, which created distress for the reclusive author and his readership.