Adalberto Garelli (10 July 1886 – 13 January 1968) received his engineering degree at age 22 and devoted his early career to developing and perfecting the two-stroke engine, initially for Fiat. When Fiat showed little enthusiasm for the technology, he left in 1911 and spent the next three years independently developing a distinctive 350cc split-single cylinder engine. After working for other motorcycle manufacturers from 1914 to 1918, Garelli won a Royal Italian Army competition to design a military motorcycle using his split-single engine.
In 1919, Garelli constructed a 350cc motorcycle that immediately set a long-distance record, covering the route from Milan to Naples — 840 kilometres — at an average speed of 38.29 km/h, ridden by Ettore Girardi. The 350cc split-single design remained in production until 1926 and made a significant impact in early Italian road racing. Many of the country's most celebrated racing figures, including Tazio Nuvolari and Achille Varzi, began their competitive careers on Garelli machines.
After World War II, Garelli shifted focus toward smaller bikes and mopeds serving the European mass market. The company's return to international competition came in the 1980s, when it re-engaged with Grand Prix motorcycle racing at the 125cc level.
The results were historic. Garelli won the 125cc World Constructors' Championship in six consecutive seasons: 1982, 1983, 1984, 1985, 1986, and 1987. The company also claimed the 50cc World Constructors' Championship in 1983. This period of dominance placed Garelli among the most successful constructors in the history of small-displacement Grand Prix competition and represented a remarkable revival for a manufacturer that had been absent from elite racing for decades.
Beyond Grand Prix racing, Garelli demonstrated the durability of its engineering through long-distance record attempts. On November 3, 1963, the company set eight world long-distance records using two 50cc motorcycles, further establishing the brand's credentials in endurance performance.
In 1982, after Garelli went out of business, businessman Rudolf Scheidt purchased the rights to the Kreidler trademark and contracted Garelli to produce mopeds under the Kreidler name until 1988, reflecting Garelli's continued manufacturing capability even as its own brand faced commercial difficulties.
The Garelli name returned to the market in 2019, the company's centenary year, with the launch of fully electric products including the Ciclone Sic58 e-bike, developed in collaboration with the Marco Simoncelli Foundation. The product was named in honour of the late Italian Grand Prix motorcycle racer Marco Simoncelli.
Garelli's place in motorsport history rests primarily on its 1980s championship dynasty. Six successive 125cc world titles in an era of fierce international competition demonstrated an engineering and competitive consistency that shaped the character of the class throughout the decade. The company's earlier influence on Italian motorcycle culture, through the careers of riders like Nuvolari and Varzi who trained on Garelli machinery, adds a further layer to its historical significance.