Launched in 1984, the Kawasaki GPZ900R (also known as the ZX900A) was the world's fist Ninja motorcycle. So groundbreaking was its design, the Kawasaki Ninja was faster than bikes with more displacement and lighter than bikes with less displacement. The motorcycle's primary advantage was its engine: the first liquid-cooled, double-overhead cam, 16-valve, inline four-cylinder that Japanese OEMs continue to utilize as the preferred sportbike engine format. The Kawasaki Ninja's 908cc engine produced nearly 115 horsepower at 9,500 rpm that propelled it to a top speed in excess of 150 mph (the first stock streetbike to do so) and to a standing quarter-mile time of 10.9 seconds.

The Kawasaki Ninja's engine, combined with its aluminum-alloy sub-frame, 16-inch front wheel, triple-disc brakes and six-speed gearbox was such an advancement in motorcycle performance that three privateer Ninjas placed first, second and third in that year's Isle of Man TT races, beating factory-supported teams from other manufacturers.

Since 1984 the Kawasaki Ninja designation has graced the fairings of numerous Kawasaki sportbikes ranging in size from 250cc to 1400cc. So ubiquitous has the name Ninja become that non-motorcyclists often refer to any sportbike, Kawasaki or otherwise, as a Ninja.

In the 1980s 600cc and 750cc Kawasaki Ninjas did battle with Honda Hurricanes and Interceptors until Honda stopped using the names and instead went to the alpha-numeric insignias (see CBR and VFR). In 1988, the Kawasaki ZX-10 (1000cc) Ninja was launched and immediately claimed the title of the world's fastest production streetbike with a top speed of 166 mph. In 1990 the Kawasaki ZX-11 (1100cc) Ninja replaced the ZX-10, upping top speed to 175 mph and retaining its top-speed title for years to come.

In 1993 Scott Russell piloted a Kawasaki ZX-7R (750cc) Ninja to a World Superbike title against Ducati's legendary 916 ridden by Carl Fogarty. From 2003 to 2008, the Ninja name was even attached to Kawasaki's MotoGP effort and its ZX-RR prototype. The GP bike struggled, however, never winning a race before Kawasaki's withdrawal from MotoGP racing.

Of all the Kawasaki Ninjas, the diminutive Kawasaki Ninja 250 is one of Kawasaki's all-time best selling motorcycles. Since 1986 the liquid-cooled, vertical twin-cylinder 250cc Ninja has been a part of Kawasaki's model line-up and, with minimal competition from other manufacturers, has become the default sport-style bike for beginner riders. The Kawasaki Ninja 250's combination of sporty looks, low retail price, light weight and non-intimidating performance make it the perfect motorcycle for novice riders to hone their skills before upgrading to a larger sportbike. In 2011 Honda introduced the CBR250, a sportbike with a liquid-cooled, single-cylinder engine featuring fuel injection, to compete with Kawasaki's littlest Ninja.