The 21-year-old has signed a five-year contract after passing a medical with the Milan club.
Inter will pay an initial €40m for Hakimi with a further €5m to follow in bonuses. The player will earn a net salary of €5m-per-season according to reports.
He arrives at the San Siro following two impressive seasons on loan at Borussia Dortmund in Germany.
The Moroccan international registered 10 assists and scored five goals in 33 Bundesliga appearances this term.
A lightning fast right wing-back, Hakimi is regarded as a perfect fit for Antonio Conte’s system at Inter.
A product of the Real Madrid youth system, Hakimi made 17 appearances for Los Blancos in the 2017-18 season.