The Alfa Romeo 135 Tornado was an Italian 18-cylinder radial engine designed by Giustino Cattaneo in 1934–1935.

Cattaneo left Alfa Romeo in 1936, leaving the development of the 135 to eng.

At the time of its first running in 1938 and 1939 it was one of the most powerful radial engines in the world, generating just less than 1,492 kW (2,001 hp) on 100 octane fuel, but the standard fuel available was 87 octane, with which the 135 developed 890–1,190 kW (1,200–1,600 hp).

Although many mechanical defects were addressed during testing, it suffered from overheating and vibrations so seriously that it was rejected from service.

Further development resulted in the Alfa Romeo 136, but this remained a paper project before the Armistice in September 1943 intervened.