The confirmation came less than 24 hours after the former Paris Saint-Germain star and the France team were knocked out of Euro 2024 by Spain in the semi-finals.
Mbappe, who will wear the number 9 shirt, will be presented at the Bernabeu at midday (1000 GMT) on Tuesday and will be welcomed by Real president Florentino Perez for the signing of his five-year contract, the club announced on Wednesday.
France's captain had a disappointing Euro 2024 and was hampered by breaking his nose in his country's opening match against Austria and missed a late chance to equalise in the 2-1 defeat to Spain on Tuesday.
Mbappe is due to have his first competitive game for the Spanish and European champions when they open their La Liga defence against Real Mallorca on the weekend of August 17/18, with his first taste of the Bernabeu coming a week later when Madrid host promoted Real Valladolid.
Mbappe joins Real as a free agent on a reported annual salary of 15 million euros ($16.2 million), with bonuses attached to his arrival in the Spanish capital of over 100 million euros.