Nigerian forward Onyekuru joined Everton from Belgian team KAS Eupen in 2017.
He spent spells on loan at Anderlecht and Galatasaray, helping the latter to the title in Turkey last season, and never played for Everton.
“AS Monaco is pleased to announce the signing of Henry Onyekuru from Everton,” read a statement on the Ligue 1 club’s official website. “The Nigerian offensive midfielder is committed to five seasons.”
Last season, PSG were reportedly one of the clubs interested in the 21-year-old’s signature, with Marseille, Borussia Dortmund, Napoli and Sevilla also touted as potential suitors.
There had also been a suggestion that Marco Silva would look to integrate the player this season, but especially having signed Alex Iwobi on deadline day, any way into the Toffees first team looked unlikely.