Berlusconi bought the Rossoneri in 1986 and helped the club to a hugely successful period that included five Champions League titles, eight Serie A titles and the Coppa Italia.
Berlusconi also helped AC Milan win the Coppa Italia five times, the UEFA Cup Winners' Cup twice, the UEFA Super Cup five times, and the FIFA Club World Cup three times.
Milan said in a statement: "Deeply saddened, AC Milan grieves the passing of the unforgettable Silvio Berlusconi and wishes to reach out to the family, associates, and most cherished friends to share our sympathies.