The 125cc class had been part of the Grand Prix motorcycle racing world championship since its founding in 1949, making it one of the sport's oldest categories. For most of its history the class used two-stroke engines, which allowed the small displacement category to remain genuinely competitive and technically interesting. A broader FIM policy to phase out two-stroke technology from world championship racing, already completed in the premier MotoGP class from 2003 and initiated in Moto2 from 2010, brought the 125cc category to an end after the 2011 season. The new Moto3 class replaced it in 2012 with a four-stroke, single-cylinder 250cc formula.
Moto3 machines are restricted to single-cylinder 250cc four-stroke engines with a maximum bore of 81 mm. The minimum combined weight of motorcycle and rider is 148 kg including fuel. Unlike the premier MotoGP class, Moto3 uses prototype engines rather than production-based units. No restrictions on engine configuration beyond displacement and cylinder count are imposed, leaving manufacturers flexibility within a highly constrained envelope.
Carbon brake discs are not used in Moto3; the class runs on steel discs in common with Moto2. From 2024, Pirelli became the sole tyre supplier for both Moto3 and Moto2, replacing Dunlop, which had served the class since its introduction.
When Moto3 launched, rider age limits were set at 16 to 28 years, with new contracted riders entering for the first time capped at 25. In 2014 the rules were amended to allow under-age FIM CEV Repsol Moto3 champions to compete at World Championship level; the first beneficiary of this provision was Fabio Quartararo, who had won the CEV championship in both 2013 and 2014 before his world championship debut.
Following a series of fatalities involving young riders in junior motorcycle racing classes, the FIM introduced a minimum age of 18 for Moto3 starting with the 2023 season, raising the floor from the original 16.
The class has not been without tragedy. Swiss rider Jason Dupasquier was killed following an accident during the second qualifying session at the 2021 Italian Grand Prix at the Autodromo Internazionale del Mugello. He became one of several Grand Prix motorcycle racers in various classes to lose their lives in the modern era.
In 2024, Colombian rider David Alonso became Moto3 World Champion, making him the first Colombian rider to win a World Championship in Grand Prix motorcycle racing history. The class has consistently served as the entry point for riders who later reached the MotoGP class, and a Moto3 title is widely regarded as the initial credential for the sport's premier level.
Rules and regulatory changes in Moto3 are decided among four entities: the FIM, Dorna Sports, the International Road Racing Teams Association (IRTA), and the Motorcycle Sport Manufacturers Association (MSMA). Dorna holds a tie-breaking vote in cases of disagreement. In matters of technical change, the MSMA can act or veto by unanimous vote among its members.
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