Bishop of Milan (born c. between 337 and 340 – died 4 April 397).
Became one of the most influential ecclesiastical figures of the 4th century. He was one of the four original Fathers of the Church.
Ambrosius is traditionally credited but not actually known to have composed any of the repertory of Ambrosian chant (also known as "antiphonal chant"). He composed several original hymns as well, and is credited with introducing hymnody from the Eastern Church into the West.