The SIAI S.58 was an Italian flying boat fighter prototype of the 1920s designed and manufactured by SIAI. It was a wooden, single-seat, single-bay biplane with a hull based on that of the SIAI S.51 racing flying boat which had participated in the 1922 Schneider Trophy race. The S.58's engine, a 221-kilowatt (296-brake horsepower) Hispano-Suiza HS 42 V8 driving a pusher propeller, was mounted on struts above the hull. SIAI proposed an armament of two fixed, forward-firing 7.7-millimeter (0.303-inch) Vickers machine guns mounted on the hull on either side of the cockpit. The S.58 made its first flight early in the summer of 1924 and on 25 August 1924 set a world altitude record for aircraft of its type by reaching 5,831 meters (19,130 feet) with a payload of 250 kilograms (551 pounds).

The SIAI S.58 was an Italian flying boat fighter prototype of the 1920s designed and manufactured by SIAI. It was a wooden, single-seat, single-bay biplane with a hull based on that of the SIAI S.51 racing flying boat which had participated in the 1922 Schneider Trophy race. The S.58's engine, a 221-kilowatt (296-brake horsepower) Hispano-Suiza HS 42 V8 driving a pusher propeller, was mounted on struts above the hull. SIAI proposed an armament of two fixed, forward-firing 7.7-millimeter (0.303-inch) Vickers machine guns mounted on the hull on either side of the cockpit. The S.58 made its first flight early in the summer of 1924 and on 25 August 1924 set a world altitude record for aircraft of its type by reaching 5,831 meters (19,130 feet) with a payload of 250 kilograms (551 pounds).