The BMW K100 is a family of four-cylinder 987 cc motorcycles that were manufactured by BMW from 1983 to 1992.

As the 1970s came to an end, BMW faced three problems from developing its flat-twin boxer engine further:

In combination, this meant that BMW's marketing to users of a superior bike, allowing them to price at a premium, was being quickly lost, resulting in a loss of sales and market share.

The need for a quick development time scale of a clean burning four-cylinder engine and the fact that Honda had developed a flat-four boxer for the GL1000 Gold Wing, guided the design team led by Josef Fritzenwenger and Stefan Pachernegg to an existing liquid-cooled Peugeot car engine.

To speed development but improve the engine, the team made two key choices. Firstly, as a car engine, it was relatively large (most specifically wide, but also tall) compared to a motorcycle engine. As BMW needed something different from every other manufacturer, the choice was made to lay the engine flat in the frame to keep the centre of gravity low and improve the bike's handling. This is known as a longitudinal four because the crankshaft is in line with the direction of travel of the motorcycle. This configuration, an inline four cylinder engine with a longitudinal crankshaft had not been used since pre-WWI-era motorcycles such as the FN Four and Pierce Four, and overcame the problem of necessitating a horsepower-robbing 90-degree turn to the driveshaft. The second development took place around engine management, with Bosch L-Jetronic fuel injection, and later, Motronic fuel injection replacing carburettors, increasing power, broadening and smoothing the powerband and reducing fuel consumption.