The 125cc class had been part of Grand Prix motorcycle racing since the inaugural 1949 FIM World Championship. For decades, it formed the entry point for junior talent, producing some of the sport's greatest riders before they progressed through the 250cc class and on to the premier 500cc and eventually MotoGP divisions. However, the FIM and Dorna Sports concluded that the aging two-stroke 125cc format needed to be replaced with a more modern and sustainable platform.
In 2012, the 125cc two-stroke class was discontinued and replaced by the new Moto3 category. The regulations called for 250cc single-cylinder four-stroke engines with a maximum bore of 81 mm, a maximum weight of 65 kg for the motorcycle including fuel, and a combined minimum weight of 148 kg for motorcycle and rider together. The shift to four-stroke technology aligned with the direction already taken in the Moto2 class two years earlier.
Moto3 machines are purpose-built prototype motorcycles restricted to a single-cylinder four-stroke engine of no more than 250cc displacement. Unlike Moto2, which uses a spec engine, Moto3 permits multiple engine suppliers to compete — traditionally Honda, KTM, and other manufacturers have fielded Moto3 machinery. The class retains relatively open prototype rules while controlling costs through the engine and weight parameters.
Carbon brake discs are not permitted in Moto3. From 2024, Pirelli became the sole tyre supplier for Moto3, replacing Dunlop. From 2019, Moto3 adopted the same knockout qualifying format used in MotoGP.
Moto3 has historically operated strict age limits to manage the participation of young riders on the international stage. Traditional limits set minimum and maximum ages for entry, with the minimum set at 16 years old. As part of a broader FIM safety response following a period of fatalities involving young riders in lower-class competition, the minimum age for Moto3 was raised to 18 starting in the 2023 season. A specific provision has allowed under-age champions of the FIM CEV Repsol Moto3 junior championship to participate at World Championship level, a rule introduced in 2014 whose first beneficiary was Fabio Quartararo, double CEV champion in 2013 and 2014.
The Moto3 class has not been without tragedy. In 2021, Swiss rider Jason Dupasquier was killed following an accident during qualifying at the Italian Grand Prix at Mugello, an incident that intensified scrutiny of safety in the junior classes and contributed to the subsequent minimum-age rule change.
Moto3 functions as the talent identification and development stage for the entire Grand Prix structure. Riders graduate from national junior championships and regional series to compete in Moto3, where the tight technical regulations and lightweight machines produce some of the most densely-packed and tactical racing in the world championship. Pack racing tactics, slipstreaming, and late-braking battles characterise a typical Moto3 race. Champions and front-runners routinely progress to Moto2 within one to three seasons.
Notable Moto3 graduates include Marc Marquez, Valentino Rossi's spiritual successor generation, and David Alonso, who in 2024 became the first Colombian rider to win a World Championship in Grand Prix motorcycle racing history.
Since 2025, Moto3 continues under the MotoGP Sports Entertainment Group umbrella following Dorna Sports' acquisition by Liberty Media. From 2027, new MotoGP-wide regulations will take effect alongside continued Moto3 operation under Pirelli tyres.