St. Patrick, the primary patron saint of Ireland, is synonymous with the Emerald Isle, having converted the largely pagan society to Christianity in the fifth century. In the centuries that have followed, legends have sprung up surrounding his life, including that he drove all the snakes out of Ireland, used the shamrock to teach the Irish about the Holy Trinity, and was captured by Irish pirates and enslaved at the age of 16.
While there is no historical evidence that he drove snakes out Ireland or ever referenced shamrocks, according to St. Patick's autobiography, he was indeed kidnapped from his birthplace in Roman Britain and forced to work as a sheep herder in Ireland for six years.
The autobiography, titled "Confessio," provides details surrounding his family, birthplace, and journey back to Ireland after escaping slavery. It began [translation via Christian Classics Ethereal Library]:
The modern-day location of the "settlement of Bannavem Taburniae" has long been contested; experts have not reached any definitive conclusion, as of this writing. As explained in "Saint Patrick Retold" by Roy Flechner:
After six years as a slave in Ireland, he managed to flee back to his homeland and reunite with his family. In one of the most famous passages of "Confessio," he tells of a dream he had that inspired him to return to Ireland and become a missionary.
In sum, while it is uncertain as to which town in Roman Britain St. Patrick was born in, historians know from his autobiography, "Confessio," that he was not Irish, nor was he born in Ireland.