Mohammad-Reza Shajarian (Persian: محمدرضا شجريان‎‎; Persian pronunciation: [mohæmːæd ɾeˈzɒː ʃæʤæɾiˈɒːn]) (born 23 September 1940) is an internationally and critically acclaimed Persian classical singer, composer and Ostad (master) of Persian music. He has been called "Iran's greatest living master of traditional Persian music." Shajarian is also known for his skills in Persian calligraphy, and humanitarian activities.