He founded a worldwide organization for Catholic laity that drew inspiration from St. Louis Marie de Montfort's Marian classic "True Devotion to Mary".
The organization would be dedicated to prayer, works of mercy, and apostolic endeavors under the patronage of the Blessed Virgin Mary, Mother of God.
In fact, he was part of the "New Evangelization" before that term was coined -- yet he was neither a Pope, a bishop, nor a priest, but a layman.
On June 11, EWTN presents a half-hour documentary on the remarkable life and times of Legion of Mary Founder and Servant of God Frank Duff. "Frank Duff: A Model of Catholic Laity" airs 5:30 p.m. CT, Thursday, June 11.
Duff was born to civil servant parents John and Susan Duff in Dublin, Ireland in 1889.
The eldest of seven children, young Frank would follow in his parent's footsteps into the same career.
At age 24, Duff began his involvement in church ministry, volunteering with the Society of St. Vincent de Paul and witnessing to Dublin's inner city poor.
In 1921, Duff founded the Legion of Mary.
Members reach out to fellow parishioners, helping families, visiting the sick, meeting weekly for prayer and fellowship, and carrying out a weekly apostolic work – all in the name of Jesus through Mary.
The Legion predates many of today's 120 canonically recognized associations of the faithful, according to the Pontifical Council for the Laity's Directory of International Associations of the Faithful.
Almost 50 years before the Second Vatican Council document Lumen Gentium laid out the Church's universal call to holiness, Duff published a prophetic pamphlet entitled "Can We Be Saints?"
It was 1916 when he wrote: "In the heart of every right-thinking Catholic, God has implanted the desire to become a saint. Yet few make a serious attempt to realize the ambition."
It would also be 50 years later that Pope Paul VI would invite Duff to be a lay observer at the Second Vatican Council.
He was given a standing ovation from the bishops convened there during the Council's fourth and final session.
Frank Duff went home to the Lord on November 7, 1980 at the age of 91.
Today, with over several million members worldwide, The Legion of Mary's impact in the service of the Church has been immense and its founder is now a candidate for sainthood.