Saint Patrick is now known as the patron saint of Ireland, but he in fact was not Irish. He was born somewhere in Roman Britain, but scholars are divided as to where. He lived in the 5th century, and arrived in Ireland as a slave having been captured by pirates.
He was captive for six years, during which he converted to Christianity. He eventually left Ireland, studying further in Britain and France. He eventually returned to Ireland as a missionary, wishing to convert and baptise the pagan Irish to Christianity.