He is honoured as a Saint in the Catholic Church and his feast day is April 23.

According to the writings of Ennodius, bishop of Pavia in early 6th-century, Marolus was born on the banks of the Tigris in Mesopotamia.

[1] Probably due to the persecutions by Shapur II, Marolus moved before 380 to Syria where he grew up.

He later moved to Rome, where he became friend of Pope Innocent I, and finally to Milan, where he became the bishop in 408.

[3] Marolus died on April 23, 423, and he was buried in the Church of Saint Nazarius and Celsus in Milan.