The deal, confirmed by press, secures the services of the French international, who was due to become a free agent at the end of the season.
Maignan has been a key figure for Milan since his arrival, providing consistency between the posts and helping the club maintain their competitive edge in Serie A. The agreement signals the club's commitment to retaining their core players amid a period of squad evolution and future planning.
Chelsea were reportedly monitoring the situation and considered a free transfer move at the end of the current contract, but nothing materialised, with Milan moving quickly to prevent the goalkeeper from leaving.
Maignan's renewal ends speculation over his future and reassures fans of stability in the goalkeeping position.