Austrian composer and musicologist, highly esteemed as an authority on Byzantine music.

A pupil of Guido Adler in musicology and of Arnold Schoenberg in composition, Wellesz taught at the University of Vienna (1930–38) before settling in England (1939), where he became an influential teacher at the University of Oxford. His scholarly work ensured his importance in the history of musicology. He was influenced by Schoenberg's 12-tone method of composition, but tonality remained a shaping force in his work, which includes operas, ballets, nine symphonies, chamber music, and Roman Catholic church music.