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Yamaha RZ350 (RD350LC (Liquid Cooled) in some countries) is a motorcycle powered by a twin cylinder two-stroke engine, reed valved 347 cubic centimeter engine. The bore and stroke are 64x54 mm. It produces 30.4 ft·lbf (41.2 N·m) of torque at 7500 rpm. Coming out in 1980, it was the evolution of Yamaha's popular and well known RD350. Production was carried on into the 1990s and the engine was used in Yamaha's Banshee ATV until its final model year in 2006.

RZ350 is now a sought after collectors bike, due to it being the last road going two-stroke motorcycle in America. It is also raced extensively in Vintage racing leagues, as well as its own racing leagues, often dubbed "RZ cups" in Europe. A perfect bike for those just learning to race or those with nostalgic ties to the old days of racing.

This bike was only sold in the United States for two years 1984-85. It was not sold to the public after because of emission regulations after 1985. The exhaust had a variable valve called the Yamaha Power Valve System (YPVS) that was controlled by a basic computer. The YPVS could adjust the height of the exhaust port and thusly affect the exhaust port timing. The result was more lower RPM torque while retaining high RPM power. Many of these bikes were salvaged because of the interchangeability of many of the major engine components with the Banshee ATV. There was a 500 cc version called the RZ500. (It was this bike that gave the RZ its name, while the 350 was more of a basic, beginners bike. It came in a red on white color scheme.) It was a twin-crank V4 cylinder version (much like the GP bikes of the era) and was a quite different bike with the Kenny Roberts black on yellow colors as an option.

In many countries, these bikes were known as RDs, but in North America and Australia they were called the RZs.

Note: in Australia, the Yamaha RD series (RD125,RD250,RD400) from which the later RZ/RD were descended, were first released in the 1970s as air-cooled 2 strokes. Later, (1981?), the bikes had a major redesign using ideas Yamaha gained from 2-stroke GP and production race experiences. They also became liquid cooled and had an 'LC' appended to the name to designate this eg: RD350LC - some people referred to them as "Elsie". The most common capacities sold in Australia were 250cc (maximum capacity allowed for new road riders) and 350 cc and were very popular with production racers. The first models of theses were supplied without a thermostat in the cooling system and many were retro fitted as they ran too cool even in Australia The name changed to RZ in (Australia at least), with the introduction of the variable exhaust valve (YPVS - Yamaha Power Valve System) design in 1983 on the 'K' model.