The Ducati ST is a series of sport touring motorcycles produced by Italian manufacturer Ducati. The ST series includes models such as the Ducati ST2, Ducati ST4 and Ducati ST4S. The ST series is a combination of sport and touring motorcycles, with the ST2 and ST4 both featuring a 904cc V-twin engine, while the ST4S has a 992cc V-twin engine. These models are designed to provide riders with a comfortable and enjoyable ride while still providing sporty performance.