Karl Ignaz Weigl (6 February 1881 – 11 August 1949) was an Austrian composer. He was born in Vienna, being the son of a bank official who was also a keen amateur musician. Alexander Zemlinsky took him as a private pupil in 1896. Weigl went to school at the Franz-Joseph-Gymnasium and graduated from there in 1899. After that, he continued his studies at the Vienna Music Academy, where he became a composition pupil of Robert Fuchs, and also enrolled at the University of Vienna, studying musicology under Guido Adler, having Anton Webern as a classmate. His only opera, Der Rattenfänger von Hameln, premiered in Vienna in 1932.[1]

When the Nazis occupied Austria, in 1938, Weigl emigrated to the United States of America, together with his second wife, musician and composer Vally Weigl (née Pick), and his son. There, he obtained a number of increasingly important teaching posts: at the Hartt School of Music, at Brooklyn College, at the Boston Conservatory and, from 1948 on, at the Philadelphia Academy of Music. He died in New York after a prolonged battle with bone marrow cancer.

Weigl wrote many compositions including symphonies, chamber music pieces including string quartets, and songs for solo piano.