Ercole Marelli founded in 1891 the homonymous company specialized in the production of motors and electrical appliances. When the company was born, it produced electromechanical appliances, 5 years later also the air agitators, today's fans. On 28 February 1900 it became a limited partnership, in December 1905 it inaugurated a plant in Sesto San Giovanni (MI) producing small electric motors, centrifugal electric pumps and transformers. Between 1906 and 1911, the number of employees increased from 500 to more than 1500. In 1915, the "Società Anonima Ercole Marelli" started the first Italian experiments in the field of ignition magnets for internal combustion engines.

In 1919, Magneti Marelli, a share capital of 7 million lire, was subscribed in equal parts by Fiat and "Società Anonima Ercole Marelli" due to the growing need for ignition magnets for the car and aviation market.

In 1920 La Ercole Marelli becomes a public limited company. In 1922 the company was inherited by Fermo Marelli, son of Ercole Marelli.

In the 1930s, the production of large machinery such as alternators and transformers, control systems for rolling mills for the world's largest steel producers, propulsion machinery for ships and equipment for trains, electric pumps for waterworks and reclamation works was greatly enhanced. Before the Second World War, employees exceeded 5000 people.

In the 1960s, Ercole Marelli exports high-powered locomotives for the Chile railways and diesel-electric locomotives for the Argentine railways, reaching maximum employment with 7100 employees. Its products, which were technologically advanced at the time, are present in many realizations for mass transport, such as traction drives for the Milan Metro; subsequently, it was the first Italian company to offer power drives for chopper locomotives. Starting in 1968, the company had to restructure to cope with the drop in prices in the electromechanical sector. In March 1981 it was put into liquidation. In 1993 it was incorporated into the Firema group.