Liberty V12 engine photographed at Hendon in 2012.

The Liberty L-12 was an American 27-litre (1,649 cubic inch) water-cooled 45° V-12 aircraft engine of 400 hp (300 kW) designed for a high power-to-weight ratio and ease of mass production. It was succeeded by the Packard 1A-2500.

There were 20,478 engines produced between 1917 and 1919. Only a few engines made it to France before the war ended.