Pellegri, who turns 17 in March, had been in negotiations with Italian champions Juventus but the Riviera side pushed through a five-year deal on Saturday.
Pellegri has long been compared to 19-year-old French striker Kylian Mbappe who was loaned out by Monaco to Paris Saint-Germain this season after a whirlwind first full season in Ligue 1.
“I was very quickly convinced by the Monaco project that allows young people like me to progress and blossom in the future,” said Pellegri, who matched a Serie A record when he made his debut at the age of 15 years.
“I will work hard to become an important player for the club in the future.”
Pellegri also made history by becoming the youngest scorer in Serie A last May in Roma legend Francesco Totti’s farewell match and this season became the youngest to net a brace.
He has scored three goals in ten appearances for his hometown club Genoa where his father Marco is a member of the coaching staff.
As part of the deal Genoa will receive 10 per cent of any future transfer fee over 40 million euros, according to reports.
“We’re very happy to welcome Pietro to Monaco. He’s a very young player who already possesses experience in Serie A,” said Monaco vice-president Vadim Vasilyev.
“He has great qualities, great potential and we’re convinced that with time and a lot of work here he’ll become an important player.”
The under-19 Italy international will reportedly earn one million euros for his first season, but he insisted: “I am not interested in money, as I just want to play and enjoy my football.
“If people had told me a year ago that I’d be moving from the Genoa youth team to Monaco, I’d have thought it was a dream, but this dream has come true.”
Genoa posted a farewell message on Twitter: “Yesterday, today, tomorrow … our home is your home. Proud of you, of the values you showed and of how you grew up in Cantera. We wish you a great career, Pietro! #Pellegri.”
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