LSM is the acronym for Landing Ship Medium, an amphibious assault vessel in the U.S. Navy in World War II. The LSM was a flat-bottomed ship with bow doors that could swing open, allowing for direct beaching and unloading of cargo.

The LSM had a maximum carrying capacity of 165 tons. It could carry five Medium or three Heavy Army tanks, but it was used to transport all types of vehicles and artillery as well as construction material and troops. It was 203′-6″ in length and 34′-6 1/2″ in breadth. Its draft, at full load, was 4′-3″ forward and 7′-2 3/4″ aft.

The ship was powered by two diesel engines, either Fairbanks Morse or General Motors, each providing 2880 horsepower at 720 RPM continuous duty (and 3600 horsepower at 800 RPM emergency duty). The design speed was 13 knots seagoing and 14 knots landing.

The LSM could carry about 163 tons of diesel oil, giving it a cruising radius of 5,000 nautical miles at 7 knots or 3,500 nautical miles at 13 knots. The original design of the LSM called for six 20mm anti-aircraft guns, but a later redesign replaced two of them with 40mm AA guns.

558 LSM-1 class ships were built for the Navy in 1944 and 1945, most of which were used in the Pacific. No LSM-1 class ships survive in the original configuration.

in 1998, the Amphibious Museum of the Americas found and restored USS LSM-45 and donated it to the National Naval Museum in Omaha, Nebraska. In 2003, the restored LSM-45 was redonated, this time to the Museum of the Marine at Camp Lejeune in Jacksonville, NC. The Museum of the Marine scrapped LSM-45 some time between 2010 and 2014.