Mousetrap was an anti-submarine rocket launcher used mainly during World War II by the United States Navy and Coast Guard. Its development began in 1941 as a replacement for Hedgehog anti-submarine mortar. Hedgehogs were spigot-launched, which placed considerable strain on the launching vessel's deck, whereas Mousetrap was rocket-propelled. As a result, Mousetrap's four or eight rails for 7.2-inch (183 mm) rockets saved weight and were easier to install.