HMS Ruler was a Ruler-class escort aircraft carrier of the British Royal Navy during World War II. She was built in the United States as the Bogue-class carrier St. Joseph (AVG/CVE/ACV-50) for Lend-Lease to the United Kingdom. HMS Ruler served in the North Atlantic during 1944, protecting the vital flow of men and war materiel from the United States to Great Britain and to fighting fronts on the European continent. In early 1945, she transferred to the Pacific Theatre where she supported a raid on Truk and the campaign to take Okinawa.