The Savoia-Marchetti S.55 was a double-hulled flying boat produced in Italy, beginning in 1924. Shortly after its introduction, it began setting records for speed, payload, altitude and range.

The S.55 featured many innovative design features. All the passengers or cargo were placed in the twin hulls, but the pilot and crew captained the plane from a cockpit in the thicker section of the wing, between the two hulls. The S.55 had two inline contra-rotating propellers, mounted in tandem. The engines were canted sharply at an upward angle. Two wire-braced booms connected the triple-finned tail structure to the twin hulls and wing.