Clarissa Oakes (titled The Truelove in the United States) is the fifteenth historical novel in the Aubrey-Maturin series by British author Patrick O'Brian, first published in 1992. The story is set during the Napoleonic Wars and the War of 1812.

This novel constitutes the third of a five-novel circumnavigation of the globe; other novels in this voyage include The Thirteen Gun Salute, The Nutmeg of Consolation, The Wine-Dark Sea, and The Commodore.

Glad that the penal colony is behind him, Captain Aubrey discovers a stowaway prisoner aboard near Norfolk Island. He deals with her before he allows the cutter from the governor at New South Wales to deliver his new orders to handle a political situation on a Pacific island. En route, Maturin learns the key to finding the high level agent giving British information to the French, while Aubrey addresses the unhappy crew of Surprise.

One reviewer finds this novel a pure joy to read as it shares unmistakably original insights into the mysteries of the world. "His books add up to a portrait of an entire world, containing every single aspect of human life." Specifically, the title character Clarissa Oakes "gives O'Brian a chance to explore their [Aubrey and Maturin's] characters in exceptional depth." One reviewer compared O'Brian's writing style to that of several famous writers, considering that he has left C S Forester far behind, and is "one of the best storytellers afloat," with use of nautical detail that is "unalloyed, unapologetic and absolutely right." Another called it "intelligent escape" as reading material, while another found that it "will delight fans."