Operation Chastity was a World War II plan by the Allies to seize Quiberon Bay, France, enabling the construction of an artificial harbor to support Allied operations in Northern France in 1944. The artificial harbor was not developed, as the US VIII Corps failed to capture German-held areas that threatened the port. By the end of August 1944, Allied forces had captured all of Brittany except for the critical areas, preventing the further development of the operation. Following the capture of Antwerp and its port facilities in early September 1944, Operation Chastity was officially cancelled on 7 September.