Credited with bringing Roman Catholic Christianity to pagan Ireland in about 389-461...he is the Patron Saint of Ireland. And, with the publication of the book by Thomas Cahill, How The Irish Saved Civilization, St. Patrick may be the key person God used to bring this about.
He was born in about 385 AD in Britain (what is now Wales?) with the birth name of Maewyn Succat. His father was a wealthy alderman under Roman rule (and a Christian, a Deacon); his grandfather may have been a Catholic Priest. He was captured by pirates/kidnappers in 401AD at age 16 and sold into slavery in Ireland. He then called himself Patricius.
For the next 6 years, he served as a shepherd for an Irish Chieftain in Ulster northeastern Ireland. It was during this time of shepherding solitude that he really began to pray prodigiously. He began to discern or hear what he thought was the voice of God. One night the voice told him, "Your hungers are rewarded: you are going home". That night, he slipped away from his master, escaped at age 22 (after 6 years of slavery), made his way 200 miles to a ship, and returned to Britain. Drawn to the priesthood, he entered a monastery in Gaul (France); and he eventually became ordained as a priest. At age 40, he had a dream in which he believed God commanded him to go back to Ireland to convert the Irish to Christianity. In 435AD, he was sent to Ireland by Pope Celestine I as a missionary (note: there were already some Christians in Ireland).
He resented the scornful attitude of British clergymen toward the Irish. His efforts were opposed by many British clergymen. In his missionary role, he had the advantage of knowing the native Irish language and having a genuine love for the Irish people. During some 30 years of his life (in Ireland), he is said to have founded more than 300 churches and baptized more than 120,000 persons. In order that Scripture be read, he introduced efforts at literacy to the heretofore illiterate nation of Ireland. The monks and priests had to be able to read and copy books. That nation went from illiterate to being a bastion of literacy in only two generations (about 32-40 years...435-475AD). Ireland would thereby become the building and growing repository of active Western civilization. Europe was going down the tubes, as follows!
At about the time Patricius was returning to Britain at age 22 (407AD), the Gothic barbarians flooded across the frozen Rhine River and plundered the civilized world...even sacking Rome in 410AD. The barbarians ravaged Europe for about 100 years...destroying much of Western civilization. But, because of the prodigious copying of literary works by the Irish monks, much of written civilized Western thought was saved. The monks eventually seeded this thought back into European culture as the West was rebuilt from around 500AD onward. (I'm indebted to Frank Chapelle's op ed article in The State newspaper of 17 March 2003 for a lot of this information.)
Legend has it that: (1) he charmed the snakes of a snake-infested Ireland into the sea so that they were drowned (but the Ice Age had ridded Ireland of snakes; so, this is a symbolic legend of the driving out of paganism). And, (2) in his missionary teaching, he used a three-leaf shamrock to illustrate the Christian doctrine of the Trinity. Modern St. Patrick's Day is March 17th, the day of the death (17 March 461AD) of the 76 year old priest who became known as "St. Patrick" ; and, ironically, it currently celebrates alcoholic drinking, partying and debauchery!!