Fifth-century bishop known as the "Apostle of Ireland"

This clue leads to St. Patrick. The sections below explain what it refers to, why it matches the clue, and why it may be appearing in the current trend cycle.

Saint Patrick was a fifth-century Romano-British Christian missionary and bishop in Ireland. Known as the "Apostle of Ireland", he is the primary patron saint of Ireland, the other patron saints being Brigid of Kildare and Columba. He is also the patron saint of Nigeria. Patrick is venerated as a saint in the Catholic Church, the Lutheran Church, the Church of Ireland, and in the Eastern Orthodox Church, where he is regarded as equal-to-the-apostles and Enlightener of Ireland.

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Saint Patrick fits because he was the fifth-century Romano-British missionary and bishop who became the primary patron saint of Ireland, earning the title "Apostle of Ireland" for converting the island to Christianity.