Colmán (d. 676) of Lindisfarne, abbot, bishop, and successor to Fínán (qv) (d. 661) and Áedán (qv) (d. 651), was born around the beginning of the seventh century. He is chiefly known for his advocacy of the Celtic dating of Easter at the synod of Whitby (664), as related by Bede (‘Historia ecclesiastica’, iii, 25–6). The opposing Roman faction was led by Wilfrid, the synod having been convened and presided over by Oswiu, king of Northumbria, sometime in May/June, soon after the solar eclipse of 1 May and the plague that ensued. Wilfrid won the argument, partly by contrasting the relatively small and isolated Celtic party with the universal Roman and western church. Oswiu ruled in favour of the Roman dating of Easter, thus ensuring the eventual unity of observance in this and other matters in the whole of the English church.
Colmán thereupon resigned his bishopric and returned to Iona, taking with him the Irish and some English monks from Lindisfarne, which thereafter was ruled by an abbot till 678, when it again became an episcopal centre. He departed from Iona for Ireland, taking with him the bones of Áedán. Around 667 he established a monastery on the island of Inishbofin off the west coast (Co. Mayo). Discord, however, broke out between the Irish and English monks, which Colmán finally resolved by settling the latter in a monastery in Mayo. This foundation subsequently became known as ‘Mayo of the Saxons’. Bede and Alcuin both praised the monastery for its way of life and its adherence to a non-Celtic rule. Two letters survive from Alcuin, dated between 793 and 804, to ‘Leutfred, bishop of the monastery of Mayo [Mugensis] in Ireland’ and to the monks there collectively. Bede also praised Colmán for his asceticism and spiritual life. Colmán is commemorated as bishop of Inishbofin and as a saint in the Irish tradition on 8 August in the Martyrology of Óengus (qv) (fl. c.830), and on 18 February in other sources.