Monaco completed the signing of Genoa's rising star Pietro Pellegri for a reported €25 million fee.
The 16-year-old had been linked to Juventus but instead signed on with the principality club.
"I am very happy to join Monaco. I was very quickly convinced by the project, which allows youngsters like me to progress and flourish in the future," Pellegri told Monaco's website.
"I will work hard to become an important player for the club in the future."
Pellegri tied a record as the youngest player to appear in a Serie A game in December 2016, when he debuted aged 15 years and 280 days.
"We are very pleased to welcome Pietro to Monaco. He's a very young player who already has experience in Serie A," Monaco vice-president Vadim Vasilyev said.
"He has great qualities, big potential and we're convinced that, with time and a lot of work, he will become an important player.
"This is further proof that our work in recent seasons, the results and the players who have come through in our shirt, are attracting the greatest talents in European football."