Turkey's Oncu youngest Moto3 winner at 15

Turkish rider Can Oncu has become the youngest grand prix winner in motorcycling by winning in his first Moto3 race in Valencia, which also marked his debut.

Can Oncu (C) has become motorcyling's youngest winner on his debut in the Moto3 race in Valencia. (AAP)

Turkish rider Can Oncu has won his maiden Moto3 race to become the youngest grand prix winner in motorcycling at age 15.

Making his debut at the season-ending Valencia Grand Prix on Sunday, Oncu secured the historic victory by taking advantage of crashes in front of him on a wet track at Ricardo Tormo circuit.

He started fourth and moved to third by the end of the first lap, then second-place Marco Bezzecchi crashed early in the race and leader Tony Arbolino went down with 12 laps to go.

The long-haired KTM rider almost crashed on the final lap but was able to recover to finish four seconds in front of 2018 champion Jorge Martin.

Oncu celebrated wildly with team members and twin brother Deniz, who is also a rider.

Deniz was on the pit wall late in the race and tried to get his brother to slow his pace on the treacherous track as he held a comfortable lead of nearly eight seconds during the final laps.

Oncu won at 15 years, 115 days, breaking the record held by British rider Scott Redding since 2008. Oncu also became the first rider to win on his grand prix debut since Japan's Noboru Ueda in a 125cc race in 1991.