Saint Columbanus was born in Leinster around 543 and died in 615.
He was thought to have studied in the monastery on Cleenish Island, Co Fermanagh, and entered the monastery in Bangor.
In 591 he wanted to go on pilgrimage for Christ and set out with twelve friends to travel to Burgundy.
He established monasteries at Annegray, Luxeuil and Fontaine.
The day is being marked with a Mass in Saint Patrick's Cathedral, Armagh, with Archbishop Eamon Martin presiding.
During the Mass the Archbishop will bless and commission young pilgrims from the Archdiocese of Armagh who will be going on pilgrimage to Rome and Taizé during the summer months.
Father Neil Collins, SSC, is preaching the homily.
There will also be pilgrim walks and gatherings in many parishes and communities across the country to honour Saint Columbanus.
A new pilgrim walk entitled The Way of Saint Columban has been prepared by the Columban Missionaries as an ecumenical pilgrimage with nine steps along a selected route in a local parish.
Each step consists of: a reading from Scripture, the words of St. Columban, a brief reflection, and, the Our Father.
The nine steps conclude with the litany of Saint Columban, prayers of intercession, prayer of Saint Columban and a shared Blessing.
He is remembered as one of the greatest of the Irish missionary monks and revered across parts of Europe.
