Triumph will enter the Moto2 championship as its sole engine supplier from the start of the 2019 season.
The British manufacturer will replace Honda, whose contract as engine supplier to the intermediate class expires at the end of 2018, a Dorna source confirmed to Autosport's sister title Motorsport.com.
Moto2 was born in 2010, when the category replaced the 250cc bikes, and the change came with the introduction of Honda's four-cylinder CBR 600RR engines.
Nine years after that transition, and due to a lack of interested parties, MotoGP promoter Dorna decided to search for an alternative.
According to a report in Speedweek, the first talks took place with MV Augusta, which ruled out the project on cost grounds.
A second option led to Triumph, which was delighted to get involved in a top championship.
It will supply Moto2 teams with a three-cylinder, 750cc engine that will produce around 160bhp.
The agreement between the Hinckley manufacturer and Dorna has already been signed, and it is likely to be announced during the opening round of the 2017 season on the March 26 weekend in Qatar.