The M76 Otter is an amphibious cargo vehicle developed in the late 1940s by the US Marine Corps as a replacement for the M29 Weasel.

In April 1945, the Army began developing a tracked amphibious cargo transport vehicle, and in October 1947, the prototype of the T46 amphibious cargo transport vehicle was produced.

The T46 had a boat-shaped lower body with an enclosed upper body mounted on a suspension system with pneumatic tires suspended by torsion bars and a retractable screw.

The upgraded T46 prototype was given the new designation T46E1, and after passing tests that began in November 1949, production began in January 1951.

The USMC Ordnance Department, which was interested in the T46E1, requested further road testing of the vehicle. After tests on dry lakes, sand dunes, and muddy terrain were conducted, the vehicle was given the official designation M76 Amphibious Cargo Transporter and the nickname Otter in March 1953.

The M76 was originally developed as a vehicle for use in amphibious operations, but after the war, large-scale amphibious battles almost ceased, so its use was limited to soft terrain and areas with deep snow. However, during the Vietnam War, the low ground pressure provided by the wide tracks allowed it to be used for transporting vehicles to bases in swampy areas and for patrol missions.