The Ducati Monster (called Il Mostro in Italian) is a motorcycle designed by Miguel Angel Galluzzi and produced by Ducati in Bologna, Italy since 1993. It is a naked bike, characterized by an exposed engine and frame. The purposeful and considered use of the trellis frame in the Ducati Monster is an integral part of the motorcycle's design allowing for both aesthetic appeal and for structural efficiency. In 2005, Monster sales accounted for over half of Ducati's worldwide sales. Ducati motorcycles use almost exclusively 90° V-twin engines, which they call L-twins, with desmodromic valves, and tubular steel trellis frame, features designed by Fabio Taglioni (1920–2001).
The Monster line has had numerous variations over the years, from entry level 400 cc (24 cu in) bikes up to top of the line 160 hp (120 kW) multivalve, water-cooled superbike-engined versions, with as many as nine different Monster versions in a single model year. The Monster's elemental simplicity has also made it a favorite platform for custom motorcycle builders, showcased at competitions like the Monster Challenge. Monsters eventually accounted for two-thirds or more of Ducati's output.