Egon Wellesz (1885-1974) was an Austrian-born British composer, tecaher, and musicologist who composed over 125 works in a variety of perfomance media. He was also a scholar who specialized in Byzantine music and taught at Oxford. Wellesz was a student of composer Arnold Schoenberg and his collection contains many of Schoenberg's published works.

Wellesz was born in Vienna on 21 October 1885 and began the study of music at age seven. He initially entered Vienna University in 1904 to study law, but later changed his major to musicology. After studying privately with Arnold Schoneberg in 1905 and 1906, he received his Ph.D. in 1908. That same year, Wellesz married Emmy Stross, with whom he had one child, Elisabeth, in 1912.

The first performance of Wellesz's opera Princess Girnara was in 1921 at Frankfurt/Main. Wellesz joined the faculty of the University of Vienna in 1929 and also continued to compose operas and ballets as well as participating in several lecture series. He was awarded an honorary doctorate at Oxford in 1932. In 1938, he moved to Oxford full time, emigrating from Austria at the time of the Nazi German occupation. He was a fellow at the University of Oxford in 1939.

Wellesz continued to compose until suffering a stroke in 1972. He also served as a lecturer at Oxford and received numerous awards including Commander of the Order of the British Empire in 1957 (he had become a British citizen in 1946) and the Great Australian State Award in 1961.

Wellesz died 8 November 1974 at the age of 89.