The Suzuki RE5 is a motorcycle with a liquid-cooled single-rotor Wankel engine, manufactured by Suzuki from 1974 to 1976. Apart from its unusual engine, the RE5 is mostly a conventional roadster, albeit with some peculiar styling details thanks to Italian industrial designer Giorgetto Giugiaro.

Compared to piston engines, rotary engines are smooth, light, and compact with high power relative to displacement. Although these attributes are highly beneficial to motorcycles, Wankel-engined bikes remain something of a rarity, even though the rotary engine had once been touted as the future of motorcycling.

Suzuki's RE5 was one of the very few Wankel-engined motorcycles ever produced. Other manufacturers whose bikes reached production include: DKW, Norton and Van Veen (who used a derivative of the NSU/Audi engines developed for Citroën). Hercules also produced a motorcycle with a Wankel engine, the Hercules W-2000, that was the first rotary-powered motorcycle.

All four major Japanese manufacturers had prototypes or plans, but only Suzuki's RE5 went into production. Yamaha showed their twin-rotor RZ-201 machine at the Tokyo Motor Show in 1972, while Kawasaki tested a prototype as, allegedly, did Honda.

RE5 project chief Shigeyasu Kamiya stated that Suzuki had considered a rotary-powered motorcycle in the mid-1960s. Research and development continued till the end of that decade, leading to the signing of a technical licence with NSU in November 1970, Suzuki being the 20th firm to do so. As a pioneer of rotary development, Suzuki engineers designed and produced numerous special machines for the rotary production process. Of these, ten were particularly notable and included the machine to cut the trochoid block. Suzuki holds twenty patents in plating, as considerable research went into the composite electro-chemical materials (CEM) used to plate the rotor housing. Prototypes testing took two years. The bikes were launched in 1974. Suzuki enlisted astronaut Edgar Mitchell, to introduce and endorse the bike. A number of motorcycle publications were given a lavish week-long opportunity for test riding. This RE5's warranty was unusually comprehensive, with a full engine replacement for any engine problem within the first 12 months or 12,000 miles (19,000 km).

Despite having only a single rotor, the RE5's engine was mechanically complex and its numerous subsystems made for a heavy motorcycle. Rotary engines produce a lot of heat, and the RE5 had water- and oil-cooling, and double-skinned exhaust pipes. Ignition was CDI, with two sets of ignition points actuated via vacuum and rpm sensors, to light a solitary NGK spark plug. Three oil reservoirs served the sump, gearbox and total loss tank. Separate oil pumps fed (respectively) the main bearings and the inlet tracts (to lubricate tip seals). The throttle controlled both the primary carburetor butterfly and a second valve in the inlet manifold of the secondary throat (the "port" valve), as well as governing oil supply to the combustion chamber. Five cables in total were moved by the throttle twist grip! The carburetor was similar to that in a rotary-powered car, and was far more complicated than for normal motorcycles.

The RE5 options included: a full touring kit that included a large full fairing (with lockable "glove boxes") and windscreen, two saddlebags, a large rack and lockable top box.

Suzuki commissioned Italian industrial designer Giorgetto Giugiaro for the RE5 styling. The "tin can" instrument cluster encompassed the usual lights and a low-fuel warning light, total loss oil tank light and digital gear indicator. The tubular "can" motif was also used in the tail light, and spherical indicator lights finished off the "rotary" theme.