The beatification of Fr John Sullivan at Gardiner Street Church in North Dublin marked the first time such a service has ever been held in Ireland.
Cardinal Angelo Amato, who conducted the service, said: "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."
Born in 1861 and raised Protestant, Fr Sullivan attended Portora Royal School in the Co Fermanagh town of Enniskillen before converting to Catholicism during his thirties and joining the Jesuit order in 1900.
Following the beatification ceremony, Fr Sullivan will be referred to as "Blessed" and the occasion will now be celebrated annually on 8th May. The move is one of several steps in the process of declaring someone a saint.
Relics relating to him, including the "Sullivan Cross" which he would take with him when visiting the sick, were also blessed during the service,
Fr Sullivan taught at Dublin's Clongowes Wood College. He died aged 71 in 1933.