Ambrose of Milan (Latin: Aurelius Ambrosius; c. 339 – c. 397), venerated as Saint Ambrose, was a theologian and statesman who served as Bishop of Milan from 374 to 397. He expressed himself prominently as a public figure, fiercely promoting Roman Christianity against Arianism and paganism. He left a substantial collection of writings, of which the best known include the ethical commentary De officiis ministrorum (377–391), and the exegetical Exameron (386–390). His preachings, his actions and his literary works, in addition to his innovative musical hymnography, made him one of the most influential ecclesiastical figures of the 4th century.

Ambrose was serving as the Roman governor of Aemilia-Liguria in Milan when he was unexpectedly made Bishop of Milan in 374 by popular acclamation. As bishop, he took a firm position against Arianism and attempted to mediate the conflict between the emperors Theodosius I and Magnus Maximus. Tradition credits Ambrose with developing an antiphonal chant, known as Ambrosian chant, and for composing the "Te Deum" hymn, though modern scholars now reject both of these attributions. Ambrose's authorship on at least four hymns, including the well-known "Veni redemptor gentium", is secure; they form the core of the Ambrosian hymns, which includes others that are sometimes attributed to him. He also had notable influence on Augustine of Hippo (354–430), whom he helped convert to Christianity.

Western Christianity identified Ambrose as one of its four traditional Doctors of the Church. He is considered a saint by the Catholic Church, Eastern Orthodox Church, Anglican Communion, and various Lutheran denominations, and venerated as the patron saint of Milan and beekeepers.