St. Hilary of Poitiers, known as the “Doctor of the Divinity of Christ,” was a 4th-century bishop and theologian. Born in the Roman Empire, he initially embraced pagan philosophy before converting to Christianity. As bishop of Poitiers, he strongly opposed Arianism, a heresy that denied the divinity of Christ. Hilary’s writings, particularly his work De Trinitate, helped clarify and defend the doctrine of the Trinity. He was exiled for his beliefs but later returned to continue his defence of orthodoxy. St. Hilary is honoured as a Doctor of the Church and is celebrated on January 13 for his theological contributions.

The Canadian Conference of Catholic Bishops (CCCB) has decreed that this is a Holy Day of Memorial (Optional) to be observed in Canada.