22-year-old Ganna has ridden for UAE Team Emirates for the last two seasons. He won the under 23 Paris-Roubaix in 2016 and won the Individual Pursuit world title on the track in 2016 and 2018.
He recently finished second to Gianni Moscon in the Italian national time trial championships and is currently competing with Italy in the track World Cup in Paris.
"It’s a dream to sign for Team Sky. It’s a very impressive team and everyone in cycling is used to seeing them winning the big races," Ganna said.
"I hope I can continue to develop and improve on my first two years on the road. I’m excited to meet up with the team for the first training camp and to start to work together. The team is really impressive in how they approach time trials and team time trials and that is an area I feel I can develop, in addition to the one-day races and one-week stage races going forward.
Ganna is Team Sky’s second confirmed signing for 2019 after Jhonatan Narvaez's arrival from Quick-Step Floors was announced on Thursday. Team Sky are also expected to sign Colombian climber Ivan Sosa but his move has been delayed by a contractual dispute between his former and current agents. Ireland’s Eddie Dunbar joined Team Sky in September after the collapse of the Aqua Blue Sport team.
Team Sky will continue to have Tour de France winner Geraint Thomas and Giro d’Italia winner Chris Froome - along with Wout Poels, Michal Kwiatkowski, Bernal and Gianni Moscon - as team leaders in 2019. Thomas signed a new three-year contract in the summer, while Bernal recently agreed a new five-year contract after his successful debut season with Team Sky.