The deal is expected to carry on for a minimum of three years, after Sky parted with British brand Rapha at the end of the 2016 season.
The new kit maintains Sky's now trademark black and blue colour way, and features... a lot of lines on the front and back.
They aren't just for show (so say Sky), they represent the team's victories over the years with the short dashes on the jersey represent one day race and stage victories, while the medium length lines represent multi day stage races.
The top long dash is for Chris Froome's Tour de France victory, while the other lower one is for Bradley Wiggins yellow triumph in 2012, "which has a special place in Team Sky history."
“We’re really excited to be able to announce this partnership between Team Sky and Castelli," said Dave Brailsford on the launch.
“Castelli will be more than a kit supplier, they will be an innovation partner. Castelli has a long history of breaking new ground when it comes to kit and design.
"We will continue to push hard to make sure our riders have the best clothing and equipment, and we’re already excited about some of the ideas Castelli are working on with us."
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