Team Sky's Mikel Landa is to switch to the rival Movistar team after signing a two-year contract.
The 27-year-old Spaniard, who missed out on a Tour de France podium by just one second in July, will race for the Spanish-based team in 2018 and 2019.
Landa played a crucial part in Chris Froome's fourth Tour de France win, helping the Team Sky team-mate in the crucial mountain stages and sacrificing his own hopes of a place on the overall podium.
Movistar general manager Eusebio Unzue said: "It's great news for us. Being still a young rider and with everything that he's shown, he should be the rider who leads Spanish cycling for the next few years."
Landa, who recently won the Vuelta a Burgos and was a stage victor in this year's Giro d'Italia, where he also claimed the king of the mountains jersey, was a top three finisher in the 2015 Giro, taking two stage wins along the way.
Landa, who has also won stages on the Vuelta a Espana, Giro del Trentino, Tour of the Basque Country and the Burgos, will challenge Nairo Quintana and Alejandro Valverde for number one billing at Movistar in 2018.