St. Maximinus was born near Poitiers, and was educated and ordained a priest by St. Agritius. He succeeded Agritius as bishop of Trier in 332 or 335. At that time, Trier was the government seat of the Western Emperor, putting Maximinus close to the Emperors Constantine II and Constans.

Maximinus strongly defended the faith against the Arian heresy. He was a close friend of St. Athanasius, harboring him during his exile from 336-338. He also received banished patriarch Paul of Constantinople and helped him return to his home.

When four Arian bishops came to Trier in 342, trying to win over Emperor Constans, Maximinus refused to receive them, convincing the emperor to reject their proposal.

In 343, he worked with Constans, Pope Julius I and Bishop Hosius of Cordova to convene the Synod of Sardica. The Arians condemned him by name as one of their staunchest opponents.

Maximinus also took part in the Synod of Milan in 345, and is also said to have presided over the Cologne Synod the following year. He sent Sts. Castor and Lubentius as missionaries to the valleys of the Mosel and the Lahn.

After his death, either in 352 or 349, his followers began honoring him. In 353, his body was buried in the church of St. John near Trier, and he is the city’s patron saint.