The USA midfielder made 145 appearances and scored 26 goals for the Blues.
Christian Pulisic has joined the growing number of players to leave Chelsea this summer after completing a move to AC Milan.
The 24-year-old midfielder has signed a contract with the Serie A giants until June 30 2027, with an option to extend for a further year.
Pulisic spent four years at Stamford Bridge after joining from Borussia Dortmund in 2019, making 145 appearances and scoring 26 goals for the Blues.
One of those goals was in the 2021 Champions League semi-finals against Real Madrid, which helped Chelsea into the final where they beat Manchester City.
The United States international also won the European Super Cup and Club World Cup with Chelsea the following season.
Pulisic, who has made 60 appearances for his country and helped them reach the knockout stages of last year’s World Cup, will link back up with former Chelsea team-mate Ruben Loftus-Cheek, who joined Milan last month.
They are among a host of senior players to leave Stamford Bridge this summer as the club rebuilds under new boss Mauricio Pochettino, with the likes of Mason Mount, Kai Havertz, Cesar Azpilicueta, Mateo Kovacic and Kalidou Koulibaly also moving on.
