Nowadays, four-wheeled vehicles are equipped with many different active control systems which enhance driver and passengers safety. In the field of two- wheeled vehicles electronic systems for the control of vehicle dynamics are still in their infancy: only a few motorbikes are equipped with ABS systems, traction control, drive-by-wire, and semi-active suspensions. More specifically, the control systems today available on the market are expected to work at their best only in-plane conditions (zero roll angle). However, it is well known that a two-wheeled vehicle is characterized by large values of roll angle, which can reach the astonishing value of 50°- 55° using high-performance racing tyres. These large roll angles obviously play a major role in the overall vehicle dynamics, and make the motorcycle dynamics very different (and much more complicated to be modelled and controlled) from the car dynamics. Hence, to move a step further in active control systems for two-wheeled vehicle dynamics, the enabling technology comes from a system capable to estimate the roll angle in a reliable way and in real-time.