The Asso XI was a family of water-cooled, supercharged V12 piston aeroengines produced in the 1930s by Italian manufacturer Isotta Fraschini, and fitted to a number of aircraft types built by CANT, Caproni and others.

Isotta Fraschini produced a long series of engines with the name Asso (Ace in English).

was a liquid-cooled V-12 engine with maximum power output in the range 670–725 kW (898–972 hp) depending on the degree of supercharging.

There were two variants, differing only in their supercharger speed: the R.C.40 ran at a little over 10 times the crankshaft speed and enabled the engine to maintain a rated power of 623 kW (835 hp) to an altitude of 4,000 m (13,000 ft) whereas the R.2C.15 held 655 kW (878 hp) to 1,500 m (4,900 ft) with a supercharger gearing of 7.

Cast aluminium head blocks were bolted to each of the two banks of cylinders, providing valve ports, guides, coolant passages and camshaft supports.