The Kawasaki Z1 is a four-cylinder, air-cooled, double-overhead camshaft, carbureted, chain-drive motorcycle introduced in 1972 by Kawasaki. Following the introduction of Honda's CB750 in 1968, the Z1 helped popularize the in-line, across-the-frame four-cylinder, a format that became known as the Universal Japanese Motorcycle or UJM.

The term "Universal Japanese Motorcycle", or UJM, was coined in the mid-1970s by Cycle Magazine to describe a proliferation of similar Japanese standard motorcycles that became commonplace following Honda's 1969 introduction of its successful CB750. The CB750 became a rough template for subsequent designs from all three of the other major Japanese motorcycle manufacturers. In 2011, the New York Times said lightning struck for Honda "with the 1969 CB 750, whose use of an inline 4-cylinder engine came to define the Universal Japanese Motorcycle."