The 27-year-old becomes the sixth new arrival at Goodison Park this summer after goalkeeper Jonas Lossl, midfielders Andre Gomes, Fabian Delph and Jean-Philippe Gbamin, and striker Moise Kean.
“Everton are recruiting with the intent to win trophies and play on the biggest stage,” said Sidibe.
“I am 100 per cent motivated and ready to help the club achieve its goals and to achieve my own individual goals.”
Sidibe played an integral part as Monaco won Ligue 1 in 2016/17 and reached the Champions League semi-finals the same season and was part of the France squad that won last year’s World Cup.
“Djibril has fantastic experience, winning titles and playing many matches in a competitive league,” Everton boss Marco Silva told the club website.
“He is a World Cup winner and he has the hunger to achieve much more in his career.”