The Ligue 1 side has moved to snap up the Brazilian attacking midfielder, who was one of the stars of this summer's Under-20 World Cup.
Monaco has secured the signing of teenage sensation Gabriel Boschilia from Sao Paulo for an estimated 7 million euros ($7.7M).
The Brazilian attacking midfielder has signed a five-year deal with Leonardo Jardim’s side.
Boschilia, who has been involved with Sao Paulo’s first-team squad for around 18 months, was a key part of the Brazil Under-20 side that finished as runner up in the World Cup earlier this summer.
"I am very proud to commit myself to AS Monaco and to have the opportunity to work at a big club,” the 19-year-old told his new club’s official website after signing.