The recruitment is a major coup for Ineos principal Dave Brailsford, who is the mastermind behind Tour de France wins for Chris Froome, Geraint Thomas and current champion Egan Bernal, clinching six of the last seven titles.
The 26-year-old emerged victorious at the Giro when favourites Vincenzo Nibali and Primoz Roglic ignored a mountain-top break and Carapaz, then with Movistar, capitalised to take the race lead, which he held all the way to the Rome finish line.
Carapaz and Brailsford both spoke of his progress in a star-studded line up.
"I feel this is a great opportunity for me to continue my development and growth as a rider," said Carapaz.
"(I'll be) working with a team that continues to go from strength-to-strength, year after year."
Brailsford said Carapaz had been a target for a while.
"We have been long time admirers of his talents as a bike rider and have followed his development closely over a number of years, as we have always marked him out as a potential member of our Team," said the Briton.
"He is obviously a fantastic climber but also has great versatility as he showed at the Giro earlier this year. He is still relatively young and I have no doubt he can develop and improve even further at Team Ineos."