The Packard X-2775 (company designation 1A-2775) was an American experimental liquid-cooled aircraft engine. The engine was constructed as a single crankcase with four banks of six cylinders in what is close to an X-configuration. The engine was an upright 60 degree vee-12 and an inverted 60 degree vee-12 sharing a common crankcase. Although technically incorrect, the engine has been characterized as two Packard 1A-1500 V-12 engines coupled with a mutual crankcase.