Saint Patrick was born Maewyn Succat, in Roman Britain sometime around the 5th century. He was from a nominally Christian family. At 16 years of age he was captured by Irish pirate and forced to work as a slave. During his captivity he turned to Christ, and his time as a slave was important for his spiritual development. Working as a shepherd, he devoted a lot of time to prayer. After six years of slavery he felt that God was telling him that it was his time to escape. He successfully escaped to England, where he studied more about Christianity.
During this time he took the name of Patrick.After several years of study Patrick headed God's call and returned to Ireland as a missionary. He was not welcomed initially, but he didn't give up. According to records he baptised thousands, converted the sons and daughters of kings, started churches, and set up church leadership.
"In the light, therefore, of our faith in the Trinity I must make this choice, regardless of danger I must make known the gift of God and everlasting consolation, without fear and frankly I must spread everywhere the name of God so that after my decease I may leave a bequest to my brethren and sons whom I have baptized in the Lord—so many thousands of people." - Patrick
(Sorry the text is highlighted in this post...I wasn't sure how to undo it!)
(sources www.wikipedia.com and http://www.crossway.org/blog/2011/03/the-life-and-mission-of-st-patrick/)