Saint Columba is known as the Apostle to the Picts, because he was the first major and successful missionary who brought the Gospel to those people. The Picts were a celtic people-group who lived in modern-day Scotland. They were known for being rather warlike, perhaps discouraging missionaries from going there previously. But around 563 Columba crossed over from Ireland to Scotland with twelve companions and began evangelizing the Pagan Picts.
Like many early British and Celtic missionaries, Columba was a monk and an abbot, forming monasteries as hubs of missionary activity in various locations. The monastery on the island of Iona is the most famous one that he established and remained in active use until the Protestant Reformation reached Scotland.
Saint Columba (or Colmcille as he’s known in Irish) is fondly remembered both in Ireland and Scotland for his missionary work. In the former he’s considered the third-greatest local saint after Patrick and Brigid of Kildare. Many churches and schools bear his name in Scotland and Canada; there is even a Pipe Band here in Massachusetts named after him.
He left behind some poetry and other writings, and his legacy (or at least that of his monastery in Iona) brought to the world the beautiful and priceless Book of Kells, a Gospel book that showcases the intricate beauty of early medieval Celtic art and illumination.
Columba is commemorated on June 9th.