Fabinho has signed a new deal with Monaco that will keep him at the Stade Louis II until 2021.
Brazil international Fabinho was linked with a move to Manchester United in August, but stated before deadline day he would be happy to stay at Monaco.
And the 22-year-old has further exemplified his commitment to the club by agreeing a new five-year deal.
Fabinho said in an official club statement: "I'm very happy to be extending my contract with Monaco, as this is the club that has enabled me to reach my potential at the highest level for several seasons.
"It's also introduced me to the Champions League, and it's hugely pleasing to be able to take part in that competition again this year, with a very fine Monaco side. I have developed a lot since arriving at the club. Today is a very special day for me."
Vice-president Vadim Vasilyev added: "We are delighted with this contract extension, because Fabinho is a fantastic player with great human qualities.
"Fabinho is now into his fourth season with AS Monaco, where he has developed greatly since arriving here. Despite his young age, he is now one of the key players in the team and I'm sure he will bring us a lot more again this season."
Fabinho is a product of Fluminense's academy and left the club for Rio Ave in 2012 without making a first-team appearance.
The versatile defender was immediately loaned to Real Madrid before joining Monaco on a temporary basis in 2013.
After two seasons on loan at the principality club, where Fabinho has now made 137 appearances, he joined permanently on a contract running until 2019.