Spain's triple world champion Jorge Lorenzo will leave Yamaha for Ducati after the 2016 MotoGP season in a move that marks the end of a fractious pairing with Italian great Valentino Rossi.
Yamaha, who extended Rossi's deal to 2018 in March, said in a statement on Monday they would announce a replacement for Lorenzo in due course. Suzuki's Spaniard Maverick Vinales is seen as a frontrunner.
Ducati confirmed separately that the 28-year-old reigning champion was joining the Italian manufacturer on a two-year deal.
Ducati won the championship with Casey Stoner in 2007 but have not won a race since the Australian left in 2010.
Rossi had two seasons there in 2011 and 2012 with just three podium finishes.
There are 15 races remaining this year, with a home race for Lorenzo next up this weekend in Jerez.
Lorenzo has won all of his titles with Yamaha, joining the Japanese manufacturer in 2008. He has racked up 41 race victories and been on the podium 99 times in 141 starts.
His relationship with nine times champion Rossi has generated plenty of headlines over the years, with the 37-year-old Italian recognising the challenge from the moment the younger Spaniard walked through the door.
At one point, Yamaha had to erect a wall to divide the garage and the two riders barely spoke to each other.
Last season culminated in Rossi accusing Honda rival and double champion Marc Marquez of helping Lorenzo win the title in a "Spanish stitch-up" at the deciding race in Valencia.
Italy's Gazzetta dello Sport website said Lorenzo would be the highest paid rider on the grid, set to earn 25 million euros over the two years.