Charles Borromeo (Italian: Carlo Borromeo, Latin: Carolus Borromeus, 1538–1584) was the cardinal archbishop of the Catholic Archdiocese of Milan from 1564 to 1584. He was a leading figure during the Counter-Reformation and was responsible for significant reforms in the Catholic Church, including the founding of seminaries for the education of priests. He is honoured as a saint in the Catholic Church and his feast day is November 4.

The son of Gilberto II Borromeo, conte (count) of Arona, and Margherita de' Medici (sister of Pope Pius IV), Carlo Borromeo was born on October the 2nd, 1538 at the castle of Arona on the shores of Lago Maggiore in northern Italy. The aristocratic Borromeo family's coat of arms included the Borromean rings, sometimes taken to symbolize the Holy Trinity.

When Borromeo was about twelve years old, his uncle Giulio Cesare Borromeo, resigned to him an abbacy (the office and dignity of an abbot). Borromeo applied the revenue from this position in charity to the poor. He studied civil and canon law at Pavia. In 1554 his father died, and although he had an elder brother, Count Federigo, he was requested by the family to take the management of their domestic affairs. After a time, he resumed his studies, and in 1559 he took his doctoral degree. In 1560 his uncle, Cardinal Angelo de' Medici, was raised to the pontificate as Pope Pius IV.