St. Patrick was a British priest who spent six years of his youth as a slave in Ireland and later returned there as a Catholic missionary. Although at first he was in danger of being martyred, ultimately his mission met with great success. His autobiography "The Confession" tells of the dreams and voices that led to his conversion and his return to Ireland to fulfill his mission.
St. Patrick was born into a wealthy British family in the late fourth century. He was captured by Irish pirates and sold into slavery. During his captivity, he became a devout Christian. He heard a voice in a dream telling him it was time to escape, so he walked 200 miles to the coast, took a ship and returned to his family. He studied for the priesthood in France before returning to Ireland. He already spoke the language, having learned it as a slave, and he adapted his Christian teachings to local culture so they would be more comprehensible to the Irish. For instance, he added the locally revered image of the sun to the Christian cross to create the Celtic cross, and he celebrated Easter using the local tradition of bonfires.
Many legends have arisen about St. Patrick. One concerns the shamrock, or three-leafed plant, which he supposedly used to illustrate the concept of the Holy Trinity. Another posits that because snakes harassed him during a 40-day fast, he banned them all from Ireland, although there is no evidence that snakes ever inhabited the island. March 17, which is supposedly the day of his death, is celebrated worldwide as St. Patrick's Day.