St. Irenaeus, a 2nd-century bishop and martyr, is recognized as one of the most significant early Church Fathers. Born in Smyrna (modern-day Turkey), he became bishop of Lyon in Gaul. Irenaeus is best known for his writings against heresies, particularly Gnosticism, which threatened the core teachings of Christianity. His most famous work, Against Heresies, emphasized the importance of apostolic tradition and Scripture in preserving the true faith. Irenaeus championed the belief in the goodness of creation and the salvation of humanity through Christ. He was martyred for his faith around 202 AD and is honoured as a Doctor of the Church.
The Canadian Conference of Catholic Bishops (CCCB) has decreed that this is a Holy Day of Memorial to be observed in Canada.