Chris Froome is to leave Team Ineos at the end of the season to join Israel Start-Up Nation, ending a decade-long partnership that produced four Tour de France wins.
Froome, Britain's most successful rider, won the Tour de France four times in five years from 2013 in the colours of Team Sky, which last year became Team Ineos.
Team Ineos boss Dave Brailsford hailed seven-time Grand Tour winner Froome as a "great champion" but said it was the right time to part ways.
He said Froome, 35, was keen to have sole team leadership but Team Ineos, with fellow Tour de France winners Geraint Thomas and Egan Bernal in their ranks, were unable to give that guarantee.
"Chris's current contract comes to an end in December and we have taken the decision now not to renew it," Brailsford said.
Kenya-born Froome said: "It has been a phenomenal decade with the team. We have achieved so much together and I will always treasure the memories.
"I look forward to exciting new challenges as I move into the next phase of my career but in the meantime my focus is on winning a fifth Tour de France with Team Ineos."
Israel Start-Up Nation will this year become the first Israeli team to compete in the Tour de France. The team, funded by Israeli-Canadian billionaire Sylvan Adams, took over the World Tour license of Swiss operation Katusha-Alpecin this year.
"Chris is the best rider of his generation and will lead our Tour de France and Grand Tour squad," said Adams.
"We hope to make history together as Chris pursues further Tour de France and Grand Tour victories, achievements that would make a serious case for Chris to be considered the greatest cyclist of all time."
After winning the Vuelta a Espana -- for the second time -- in 2017 and the Giro d'Italia in 2018 Froome held all three Grand Tour titles but his star has since waned.
He was seriously injured when he crashed at the Criterium de Dauphine in June 2019 and spent months in rehabilitation, missing that year's Tour de France.
Froome's teammate Thomas emerged as the 2018 winner of the Tour while Colombian protégé Bernal claimed the 2019 title when he was just 22.
He only returned fully to the saddle in February this year at the UAE Tour, which was cut short due to the coronavirus pandemic.
Earlier this year, Froome said his hunger for a fifth or even sixth Tour de France victory remained undiminished.
"My dream is to retire having won more Tour de Frances than any other rider," he told French daily L'Equipe.
He needs one more to equal Eddy Merckx, Jacques Anquetil, Bernard Hinault and Miguel Indurain, who have all won it five times.
This year's Tour, postponed because of the coronavirus pandemic, is set to be raced from August 29 to September 20.
Brailsford has overseen seven Tour de France wins with Team Sky and Team Ineos, with Bradley Wiggins claiming the first one in 2012.
Team Sky, backed by Rupert Murdoch's media empire, were known for Brailsford's meticulous and innovative application of "marginal gains", the theory that many small advantages in areas as diverse as wind resistance, diet and sleep quality can add up to a significant improvement in performance.
However, their image was clouded in controversy over so-called therapeutic use exemptions. A damning British parliamentary report said the team crossed an "ethical line" by using the loophole to administer drugs to enhance performance.
Sky were caught in a long-running doping controversy that began when Froome returned an adverse doping test, for elevated levels of the asthma medication salbutamol, on his way to victory in the Vuelta a Espana in 2017. He was cleared 10 months later.
Froome said that during the 2015 Tour de France a cup of urine was thrown at him following accusations he was doping. He has always maintained he is a clean rider.
Team Sky became Team Ineos last year to reflect their new sponsor, the chemicals giant owned by British billionaire Jim Ratcliffe.
They have had plenty of detractors within cycling for tactics that many believe stifle racing.
Their superior budget allowed them to employ riders who would be leaders elsewhere in a support capacity and effectively shut down attacks in the biggest races, something that has proved unpopular with many, particularly in the Tour de France.