A layman martyred at Nicomedia in 370, during a period when Arian imperial pressure fell on Nicene Christians in the East.

Saint Theodore of Nicomedia in Bithynia was a Christian layman who died for his faith in the year 370 at Nicomedia, a major city of the Roman province of Bithynia. He is remembered together with two companions, Saint Urban and Saint Medimnus, placing his death within the fourth century’s later religious conflicts, when the pro-Arian emperor Valens pressed hard against Christians who held to the Nicene faith defined at the Council of Nicaea. Beyond his companions, place, and year, no further biographical detail survives.

Quick Facts

• Died: 370 (Nicomedia in Bithynia, Turkey)
• Venerated as: Layman and martyr
• Companions: Saint Urban and Saint Medimnus

Who Was Saint Theodore of Nicomedia in Bithynia?

Theodore of Nicomedia is recorded as a layperson who died in 370 at Nicomedia together with two companions, Urban and Medimnus. This date places his martyrdom well after the persecutions of the pagan emperors had ended, during a later and different kind of pressure on Christians who held the Nicene faith under the Arian-leaning emperor Valens. The specific circumstances of his death are not detailed in the surviving record beyond the year, the place, and his two companions.

Historical Setting

By 370, official persecution of Christianity as such had ended with Constantine decades earlier, but the Church was now divided over the Arian controversy, and Valens, emperor in the East, favored the Arian position and at times used state power against bishops and communities who upheld the Nicene definition of Christ’s full divinity. Nicomedia, an important imperial city in Bithynia, was directly affected by these internal Christian conflicts turned political, making a martyrdom in this specific year and place a plausible casualty of that later, doctrinally charged persecution rather than the earlier pagan campaigns.

Why the Church Remembers Saint Theodore of Nicomedia in Bithynia

The Church remembers Theodore of Nicomedia as a reminder that persecution did not end neatly with Constantine’s conversion; internal doctrinal conflict, weaponized by an emperor with his own theological convictions, could still cost Nicene Christians their lives decades later. His witness, alongside Urban and Medimnus, belongs to this less familiar, intra-Christian chapter of the era’s suffering.

Canonization and Feast Day

There is no formal canonization on record for Saint Theodore of Nicomedia, as expected for a fourth-century casualty of the Arian conflicts. What has preserved his memory instead is the Church’s ancient, immemorial recognition, carried forward through liturgical tradition tied to the defense of Nicene orthodoxy.

What Catholics Can Learn Today

Theodore’s death under a Christian, if Arian, emperor is a sober reminder that division within the Church has sometimes carried as high a cost as persecution from outside it. His witness calls Catholics today to take seriously both the value of right doctrine and the danger of using power against fellow believers over it.

A Prayer to Saint Theodore of Nicomedia in Bithynia

Saint Theodore of Nicomedia, who held fast to the true faith of Christ even when the pressure against you came from within the Christian world itself, pray for the unity and right belief of the Church in every age. Amen.

Sources

• Roman Martyrology
• New Advent Catholic Encyclopedia, “Arianism” and “Valens”
• Socrates Scholasticus, Ecclesiastical History, on the persecution of Nicene Christians under Valens