Mohammad-Reza Shajarian (Persian: محمدرضا شجريان; Persian pronunciation: [mohæmːæd ɾeˈzɒː ʃædʒæɾiˈɒːn], 23 September 1940 – 8 October 2020) was an Iranian singer and master (Ostad) of Persian traditional music. He was also known for his skills in Persian calligraphy and humanitarian activities. Shajarian started his singing career in 1959 at Radio Khorasan, rising to prominence in the 1960s with his distinct singing style.

Shajarian's main teachers were Ahmad Ebadi, Esmaeil Mehrtash, Abdollah Davami, and Nour-Ali Boroumand. He also learned the vocal styles of singers from previous generations, including Reza Gholi Mirza Zelli, Fariborz Manouchehri, Ghamar Molouk Vaziri, Eghbal Azar and Taj Isfahani. He cited legendary Persian tar soloist Jalil Shahnaz as highly influential to his development, indicating that he often tried to mimic Shahnaz's playing style in his singing.

Shajarian collaborated with musicians such as Parviz Meshkatian, Mohammad Reza Lotfi, Hossein Alizadeh, Faramarz Payvar, Dariush Pirniakan, and Sohrab Pournazeri. He was recognized as a skilled singer in the challenging traditional Dastgah style. His works also cover some songs of Iranian ethnic music, including Mazandarani music, Azeri music, Kurdish music and Lur music.

UNESCO in France presented Shajarian with the Picasso Award in 1999 and with the UNESCO Mozart Medal in 2006. In 2017, Los Angeles Times cited him as the "Greatest living maestro of Persian classical music". After coming out in support of the Iranian Green Movement and criticizing the Iranian government, he was banned from holding concerts and releasing music.