The Supermarine S.6B was a single engine seaplane racer designed by R.J Mitchell, who designed the Supermarine Spitfire for the 1931 Schneider Cup.
The winning Schneider flight was piloted by Flt. Lt. John N. Boothman in aircraft serial number S1595 at a speed of 340.08 mph (547.19 km/h), flying seven perfect laps of the triangular course over the Solent, between the Isle of Wight and the British mainland. Seventeen days later, Flt Lt.George Stainforth in S.6B serial S1596 broke the world air speed record, reaching 407.5 mph (655.67 km/h). This lasted until 1933, when the [[Macchi M.C.72 broke the record, which still stands as the fastest piston-engined seaplane.
- Crew: 1
- Length: 28 ft 10 in (8.79 m)
- Wingspan: 30 ft 0 in (9.14 m)
- Height: 12 ft 3 in (3.73 m)
- Wing area: 145 ft² (13.5 m²)
- Empty weight: 4,590 lb (2,082 kg)
- Loaded weight: 6,086 lb (2,760 kg)
- Max. takeoff weight: lb (kg)
- Powerplant: 1 × Rolls-Royce R, 2,350 hp (1,753 kW)
- Maximum speed: 354 kn (407.5 mph, 655.8 km/h) (world speed record until 1933)
- Wing loading: 42 lb/ft² (205 kg/m²)
- Power/mass: 0.386 hp/lb (0.635 kW/kg)