Ségéne mac Fiachnaí (died 12 August 652) was the fifth abbot

Abbot of Iona

The Abbot of Iona was the head of Iona Abbey during the Middle Ages and the leader of the monastic community of Iona, as well as the overlord of scores of monasteries in both Scotland and Ireland, including Durrow, Kells and, for a time, Lindisfarne...

 of the Iona Abbey

Iona Abbey

Iona Abbey is located on the Isle of Iona, just off the Isle of Mull on the West Coast of Scotland. It is one of the oldest and most important religious centres in Western Europe. The abbey was a focal point for the spread of Christianity throughout Scotland and marks the foundation of a monastic...

 in Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 (623–652).

Ségéne was of the Cenél Conaill

Cenél Conaill

The Cenél Conaill is the name of the "kindred" or descendants of Conall Gulban, son of Niall Noígiallach defined by oral and recorded history. They were also known in Scotland as the Kindred of Saint Columba....

, the same kindred as Columba

Columba

Saint Columba —also known as Colum Cille , Colm Cille , Calum Cille and Kolban or Kolbjørn —was a Gaelic Irish missionary monk who propagated Christianity among the Picts during the Early Medieval Period...

, and he was the nephew of a previous abbot, Lasrén

Lasrén of Iona

Lasrén mac Feradaig or Lasrén of Iona was the third abbot of Iona , in succession to Baíthéne. Lasrén worked during the abbacy of St Columba and administered the monastery of Durrow for the saint in the years before attaining Iona. Like Baíthéne before him, he was a kinsman of Columba from the...

. It was during Ségéne's long abbacy that the famous controversy regarding the dating of Easter

Easter

Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

 first made itself properly felt. Ségéne is known to have vigorously defended the Gaelic dating, and put his name to a letter written by the Gaelic clergy to Pope Severinus

Pope Severinus

Pope Severinus was pope in the year 640 who became caught up in a power struggle with the Byzantine Emperor Heraclius over the ongoing Monothelite controversy.-Election and struggle with Constantinople:...

 in 638.

Ségéne also established the first Gaelic missionaries amongst the English, sending Corman and then Áedan

Aidan of Lindisfarne

Known as Saint Aidan of Lindisfarne, Aidan the Apostle of Northumbria , was the founder and first bishop of the monastery on the island of Lindisfarne in England. A Christian missionary, he is credited with restoring Christianity to Northumbria. Aidan is the Anglicised form of the original Old...

, the latter of whom, with the help of King Oswald of Northumbria

Oswald of Northumbria

Oswald was King of Northumbria from 634 until his death, and is now venerated as a Christian saint.Oswald was the son of Æthelfrith of Bernicia and came to rule after spending a period in exile; after defeating the British ruler Cadwallon ap Cadfan, Oswald brought the two Northumbrian kingdoms of...

 (who himself had spent time in exile at Iona), established a daughter house and bishopric at Lindisfarne

Lindisfarne

Lindisfarne is a tidal island off the north-east coast of England. It is also known as Holy Island and constitutes a civil parish in Northumberland...

. It is not known if Ségéne ever met Columba, but he was a vital collector/transmitter of stories about the saint.

He died on 12 August 652.