Lawless, who currently rides for the Axeon Hagens Berman development team, follows Egan Bernal, Pavel Sivakov, and Kristoffer Halvorsen in turning pro with the British WorldTour team in 2018.
Like those three, he was a stage winner at the recent Tour de l'Avenir, springing a late attack to deny Halvorsen and the rest of the bunch sprinters on stage 4. He won the ZLM Tour one-day race in April and in June he finished runner-up behind Steve Cummings in the British national championships road race, sealing the U23 crown in the process.
"One of my main reasons for joining Team Sky is that I feel it's going to be the best place for me to develop as a rider," said Lawless in a statement from the team.
Lawless is Sky's sixth signing of the transfer window – David de la Cruz and Jonathan Castroviejo are the other two – and further evidence of an investment in youth at Sky, who last year gave neo-pro contracts to Tao Geoghegan Hart, Owain Doull, and Jon Dibben.
"We first saw Chris a couple of years back and he is someone we've been keeping an eye on," said Sky's performance manager Rod Ellingworth.
"He's put in some good results this year and obviously he just won a stage at the Tour de l'Avenir so he's in good company there. He put in a really good ride at the nationals earlier in the year, not just in terms of the result but also in the way he rode. He's strong and fast, and he attacked it from the gun which was impressive.