Saint Columba, also known as Colum Cille, was an Irish abbot and missionary who lived in the 6th century. He is recognized as one of the Twelve Apostles of Ireland and is credited with spreading Christianity in Scotland. Columba is also known for founding the monastery of Iona, which became a center for the spread of Christianity and learning in the region. He is revered as a saint in both the Catholic and Eastern Orthodox traditions.