Spain's three-time MotoGP world champion Jorge Lorenzo will leave Ducati and join compatriot Marc Marquez in a stellar line-up next season at the works Honda team.
Marquez might be a five-time world champion by then with the 25-year-old 23 points clear at the top of standings after six races.
Honda Racing Corporation (HRC) announced Lorenzo's two-year deal on Wednesday in a statement.
"From 2019, Lorenzo will become teammate to four-times MotoGP world champion Marc Marquez: two great champions with great talent and high hopes that will make a stronger team and contribute to the development of HRC," it said.
The pair are the only riders to win the MotoGP championship since Australian Casey Stoner in 2011 - Lorenzo in 2012 and 2015 and Marquez in 2013, 2014, 2016 and 2017. Lorenzo was also champion in 2010.
Between them, they have 130 wins and 255 podiums in all categories.
Lorenzo, who won his titles with Yamaha but has struggled to find his form since joining Ducati last year, will replace compatriot Dani Pedrosa in the Repsol Honda line-up.
The departure of Pedrosa, who has spent his entire grand prix career with the Japanese manufacturer since his 125cc debut in 2001, was announced on Tuesday.
Lorenzo's Italian GP victory on Sunday at Mugello was his first for Ducati but came too late to make any change in his relationship with the team.
"If the pieces that I needed had arrived much earlier, now I would say to you, 'I stay in Ducati and I have now two or three victories'," the rider told MotoGP.com after the race.
"But unfortunately, they arrive too late these pieces, and now ... I win here, but it's too late, and the next two years I will be with another bike."
The 31-year-old, who also has two 250cc titles (now Moto2) to his name, looks likely to be replaced at Ducati by Italian Danilo Petrucci, who is at the non-factory Pramac Ducati team.
Ducati have already extended the contract of works rider Andrea Dovizioso, last year's overall runner-up.