The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly 3,350 cubic inches (54.9 L).

Developed before World War II, the R-3350's design required a long time to mature, and was still experiencing problems with reliability when used to power the Boeing B-29 Superfortress.

The engine is commonly used on Hawker Sea Fury and Grumman F8F Bearcat Unlimited Class Racers at the Reno Air Races.

A larger twin-row 22-cylinder version, the Wright R-4090 Cyclone 22, was experimented with as a competitor to the 4,360 in3 (71.4 L) displacement four-row, 28-cylinder Pratt & Whitney R-4360 Wasp Major, but was not produced.

Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with 20,000 lb (9,100 kg) of bombs.

This proved unwise, as the early B-29s taking off at maximum weights, in the high temperature conditions of the B-29s tropical airfields, caused overheating that was not completely solved, and the engines also had a tendency to swallow valves.

In these versions, three power-recovery turbines (PRT) were inserted into the exhaust of each group of six cylinders, and geared to the crankshaft by fluid couplings to deliver more power.

Modifications on one, Rare Bear, include a nose case designed for a slow-turning prop, taken from an R-3350 used on the Lockheed L-1649 Starliner, mated to the power section (crankcase, crank, pistons, and cylinders) taken from an R-3350 used on the Douglas DC-7.

Normal rated power of the original stock R-3350 was 2,800 hp (2,100 kW) at 2,600 rpm and 45 inHg (150 kPa) of manifold pressure.