St. Pádraig (Patrick), one of the earliest Christian missionary saints, was born into a noble Roman family from Gaul (France) or Britain in 387 AD. When Pádraig was 16, he was carried off by Irish marauders and sold into slavery. He was made a shepherd, and toiled for six years for an Irish chieftain. Prompted by an angel, Pádraig fled to Gaul and put himself under the spiritual direction of St. Germanus of Auxerre. He prayed and studied and struggled, and after almost 20 years was given a vision of Irish children calling to him: "O holy youth, come back to Erin, and walk once more among us."
The Bishop of Rome, Celestine I, directed St. Pádraig to teach the people of Ireland the way of Christ and bring them into the Church. St. Pádraig and his companions arrived in Ireland in 433 AD, during the summer, and were immediately persecuted by the Druids (Celtic priests).
St. Pádraig did spiritual battle with the Arch-Druid Lochru for the souls of the Irish people. Using a great display of sorcery, Lochru raised himself high in the air to awe the people. St. Patrick fell to his knees in prayer at this sight, and Lochru fell to his death - stripped of his demonic power by God.
Through his God-given gift to powerfully preach the Gospel and his wonder-working, St. Pádraig brought thousands into the fold of the True Faith, starting the demise of paganism on the Emerald Isle.
St. Pádraig returned to the Lord on March 17, 493 AD, after receiving Holy Unction. He laid in state for several days before burial, with a heavenly light surrounding his body.
And what about the Shamrock?
The leaf of the yellow-flowered clover so common in Ireland was used by St. Pádraig to teach the catholic orthodox doctrine of the Most Holy Trinity: one stem (God) with three leaves (Persons). He is often depicted holding up a shamrock between his thumb and first finger in icons.
"St. Pádraig, Apostle and Enlightener of Ireland" was adapted from 'The Real Saint Patrick, Bishop of Ireland', http://www.geocities.com/Athens/3374
Beannachtai na Feile Padraig / Happy Saint Patrick's Day