Priest Fr John Sullivan raised a Protestant on first step to sainthood
A Catholic priest who was raised as a Protestant has been beatified in the first such ceremony in Ireland.
Fr John Sullivan was recognised for his work with the sick and dying.
It is the first step on the road to sainthood.
Cardinal Angelo Amato said Fr Sullivan had been "exemplary" in his religious duties.
He added: "Those who knew him considered him a saint, and in my opinion he had reached a high degree of perfection.
"Even though he came from a rich family, once he became religious he was oblivious to comfort and contented himself with what was necessary," said Cardinal Amato.
The member of the Jesuit order was born in Dublin in 1861 and attended Portora Royal School in Enniskillen, Co Fermanagh.
Representatives from the school were present at the ceremony in North Dublin's Gardiner Street Church. The school's former principal Neil Morton told the BBC he hoped that it would be known as the only Protestant school with a Catholic saint.
"That epitomises the special nature of the school, and Fr Sullivan's story also emphasises the special relationship between Portora and Clongowes Wood," he said. "Portora has had a famously liberal tradition throughout its history and John Sullivan is evidence of that."
After leaving the school, he studied at Trinity College Dublin.
In 1896, aged 35, he converted to Catholicism before entering the Jesuit order in 1900.
He died in 1933, aged 71.
Saturday's ceremony was conducted by the cardinal, assisted by Archbishop of Dublin Diarmuid Martin. After the beatification, Fr Sullivan will be called "Blessed" and will be celebrated annually on May 8.
Church of Ireland Archbishop of Dublin Michael Jackson was also present.
During the ceremony relics relating to Fr Sullivan were blessed, including the "Sullivan Cross" which he would take with him when visiting the sick.
Portora's other alumni included the playwrights Oscar Wilde and Samuel Beckett.