The 29-year-old, who has been with the team since its inception in 2010, was the revelation of last year’s Tour de France, a race that set in stone his trajectory away from the Classics and towards stage racing. This year he has won the Volta ao Algarve and Paris-Nice, and hopes to go into the Tour as a protected rider behind Chris Froome.
Thomas, whose previous contract was set to expire at the end of 2016, had said he would be open to the idea of changing teams in the future if it would be beneficial to his burgeoning Grand Tour ambitions.
"Signing again was an easy decision. Team Sky feels like home. From the other riders to the staff, I love it here,” said Thomas in a statement on Monday.
"I’ve only really just started when it comes to trying to win stage races. I’m learning all the time about how to get in the best shape for them and how to lead a team.
"For me, this year started with winning Paris-Nice and is now about going to the Tour in the best shape possible to support Froomey. After the Tour we can start looking to next year and keep setting bigger and better goals. It’s about keeping that progression going, and Team Sky is the best place to do that. I’m just super happy being part of the team."
Thomas played a big role in Froome’s Tour de France victory last year and, in doing so, rode himself into the top five overall, performing above and beyond expectations in the mountains and only falling away two days from Paris.
Team Sky’s principal, Dave Brailsford underlined Thomas’ hopes to become a contender over three-weeks, and said the team would support him to unlock his potential.
“Geraint is one of the most versatile bike racers in the world. He has demonstrated this by winning on the track, in the Classics and now in stage races,” said Brailsford.
“He has gone from strength to strength and winning Paris-Nice this year was another step up. I think it gave him real confidence and now he can set his sights on developing his performances in the Grand Tours. I still believe the best is yet to come from Geraint and we will enjoy supporting him to see just how far he can go."