It was founded in 1899 in Milan as Società Anonima Officine Meccaniche to manufacture railway rolling stock and car production began in 1918.

This model was extremely successful in racing, winning top five positions in the 2-litre (120 cu in) class in 1925 and 1926 at the Le Mans but its greatest achievement was the victory in the first Mille Miglia race in 1927 where Ferdinando Minoia and Giuseppe Morandi led home an OM '1-2-3' finish at an average speed of 77.7 km/h (48.27 mph) for 21 hours 4 minutes 48 seconds.

[3] The main new product in the post-WWII era was the Leoncino (1950) a light truck in the 3.0 to 3.5 tonnes (3.3 to 3.9 short tons) range, which was an immediate success.

It became the forefather of several series of heavier but structurally similar models, namely Tigrotto, Tigre, Lupetto, Cerbiatto and Daino, launched between 1957 and 1964.

Its 10,310 cc (629 cu in), six-cylinder turbo-diesel engine produced 260 hp (191 kW), making it the most powerful road-going European truck in the early 1960s.

In 1975 it was absorbed (as part of the Fiat Group) into IVECO and the OM brand disappeared from the truck and bus markets, although it still survives as an independent forklift manufacturer.