Island Monasteries on the River Shannon

Last updated: 20 Feb 2024

A thousand years ago there was an extraordinary cluster of monasteries in the Shannon Estuary and right up the river, including the great ecclesiastical schools of Clonmacnois and Clonfert.

One of the best known was at Scattery Island, or Inis Cathaigh, in the mouth of the Shannon. This is where Senán, patron saint of County Clare, founded a monastery back in 534. And more power to St Senan because he rid the Shannon of its monster. You might not know the Shannon had a monster, but Inis Cathaigh means the island of Cata and Cata was a most fearsome creature with a horse’s mane, gleaming eyes, thick feet, nails of iron and a whale’s tail. A sort of maritime Gruffalo. Senan defeated the brute and founded his monastery in celebration. Today, you can still see that settlement through the remains of his oratory, his house, seven chapels and a round tower which, measuring 120 feet high, is one of the tallest in Ireland.

Onwards up the Shannon to the island of Inishlosky near the Tipperary-Clare border. The island was populated by monks from Montpellier in the south of France. However, shortly after they founded their church, they had to evacuate the island because of rising waters. Flooding on the Shannon has clearly been an ongoing problem since time began.

Lough Derg – the one on the Shannon, rather than the well-known pilgrim site in County Donegal – is the biggest lake on the river. It was home to three island monasteries, the most famous being Holy Island. Its Irish name ‘Inis Cealtra’ means “island of the burials” and refers to the island’s busy ‘Saints’ Graveyard.’ This fertile, 50-acre island was somewhat prior to  the 1920s when they built the power station at Ardnacrusha and the water level in Lough Derg rose – another instance of the changed landscape in which we live.

Holy Island on Lough Derg.jpg

Holy Island, Lough Derg

Holy Island’s first recorded inhabitant was a hermit named MacCriche who resided here in 555 AD and, it is said, lived upon a honey-like juice, drawn from a tree, which possessed the headiness of wine. Hermits like MacCriche didn’t necessarily just pray, meditate, bathe their bunions and smoke fish all day. They were well read, well educated, intelligent people with a good head for engineering, maths and such like. Maybe you’re trying to repair a road or build a new bridge and you hear of a hermit called Fintan who’s good at geometry. Offer him some alms and maybe he’ll help.

MacCriche was clearly onto something because within 150 years or so, two monasteries had been established on the island. The first was founded by St. Colum in the 6th century. In the 7th century, a second monastery was founded by St Caimin, a Benedictine monk. I suspect he may have been inspired to succeed due to a bad case of sibling rivalry. According to the Annals of the Four Masters, his mother had 77 children. In any case, he turned his monastery into a celebrated scholastic institution, a great centre of learning and art. Among those who reputedly studied here was St Donagh. One day Donagh decided to head out from Inis Cealtra on a pilgrimage to the Apostle’s tombs in Rome. During this long and arduous journey, he popped into a town called Fiesole, north of Florence. As chance would have it, he arrived just as Fiesole’s citizens were about to elect a new bishop. When Donagh strolled into the cathedral, the bells began to ring and the lamps and candles burst into light. Putting two and two together, the citizens figured Donagh was a pretty magical guy and elected him their bishop. Given that the citizens had drowned their previous bishop, it’s possible that demand for the job was not high.

Donagh remained Bishop of Fiesole for over half a century and became an advisor to one of Charlemagne’s grandsons. Donagh, or Donatus, remains one of the most revered saints in Tuscany and you’ll find his name in numerous churches and place names throughout the region. Now, you might scoff and say ‘what baloney’ and fair enough. Were these people real? Did Donagh exist? Did the saints exist!? I don’t know. We’re told that they did, but there’s certainly much room for doubt. And, yet, something was happening in all of these places, these monasteries, be they small island retreats or the big monastic schools. The people of Ireland used to believe in nothing but pagan gods. However, by the close of the 9th century, I think you’d be hard pushed to meet an Irishman or woman who didn’t say their bedtime prayers to anyone except the Christian God.

Part in parcel with that is a wonderful fact that if all the world’s a stage, nobody has taken all the props and scenery away. As such, Holy Island still holds a very well-preserved Round Tower, an Anchorites’ cell, a holy well, and the ruins of six churches. This was the stage on which the monks once strutted and fretted in the time of Donagh of Fiesole and such like.

You might not know the Shannon had a monster, but Inis Cathaigh means the island of Cata and Cata was a most fearsome creature with a horse’s mane, gleaming eyes, thick feet, nails of iron and a whale’s tail.

Island monasteries were also established further up the Shannon on Lough Ree and Lough Key. On Lough Key, the best known are on Holy Trinity Island and Church Island. Inchmacnerin Abbey on Church Island was supposedly founded in the 6th century AD, by Columba (Saint Colum Cille), the patron saint of Derry who brought Christianity to the Scots.

Lough Ree is apparently home to 52 islands, some little more than an acre big, some over 200 acres. I imagine the feet of monks trod upon each and every one of those 52 islands in ancient times but, in terms of what’s known, Inchmore, the largest island on the lake, was home to a fifth century hermit called Lioban, son of Lossenus. Inchbofin also traces its monastic heritage to a 5th century hermit, Rioch, and there is an outside chance that Lough Ree itself is named for Rioch. Staying on Lough Ree, Inchcleraun, also called Quaker Island, is home to the  ruins of a substantial monastic school founded by Diarmaid the Just in 560 AD, while St Ciaran, the sort of headmaster of Clonmacnoise, is credited with founding the monasteries on Hare Island and Saints Island.

Clogas Church, Inchcleraun Island 


I spent a night on Lough Ree in the summer of 2021, slumbering on a boat called Turgesius, listening to the water splashing against the hull. It became pretty stormy for a while but then came complete peace. Total silence but for the bleat of a distant sheep as the morning light blossomed. Or the cry of a gull scooting along the wind-rippled waters. It’s a haven for marsh birds – wigeon and lapwings, swans, herons and so on. I saw a very content egret rain-bathing (it wasn’t sun-bathing weather) on one of the shallow bed markers and buoys in those serene waters. It was joyous. Just quietly gliding by those lovely moisture-filled islands. You can see why those early hermits, churchmen and churchwomen embraced a place like Lough Ree, with its relatively tame isolation, and how they favoured it as place for their ascetic retreat.

The island monasteries had their hey-day in the 8th centuries, before the Vikings came in strong, but they would bounce back from those attacks. In due course, I will home in on how the Christian church had a reboot under orders like the Augustinians and the Cistercians before the tyrant king Henry VIII closed down the whole shebang in the 1540s. But, for now, I hope this tale has helped you to see how Ireland’s waterways played such a crucial role in our history from the beginning of known time to an age when the beacon of light shone from Gaelic Ireland, a beacon that would keep Christianity lit during the strange centuries that followed the fall of the Roman Empire in Europe.


Researched and written by Irish historian Turtle Bunbury, the history of Irish Waterways and their environs is the result of extensive original scholarship through the National Archives and contemporary newspapers, as well as the expertise of local historians and academic historians.


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