Cian d'Fhearaibh Bolg

Cían d'Fhearaibh Bolg, last King of the Senchineoil of Magh Senchineoil, now in County Galway.

Cían is identified as the king of Magh Senchineol, home to the Senchineoil people, who were said to be of Fir Bolg origin, a population group from Irish mythology. It was asserted by T. F. O'Rahilly that the Fir Bolg may have been inspired by both the historical Iverni and Laigin, although this is not widely accepted in Irish scholarship, these historical kindreds having no convincingly demonstrated association with the mythological one in the surviving corpus, beyond linguistic speculation. Related may have been the Fir Domnann, who settled in what is now Connacht.

The Fir Bolg of Connacht were ruled by King Aonghus mac Úmhór. Mac Fhirbhisigh states that Aonghus led his people, the Tuath mhac nUmhoir, to the coast of Galway Bay and the Aran Islands, after being driven out by warfare with "Clann Chuian and the kindred of the Gaoidhil (Gaels)." The fortress of Dún Aonghasa on Inishmore, which legend states he built, is still called after him. O'Rahilly places these events in the 2nd century BC.

Aonghus's son, Conall Caol, settled with his people in what was then the kingdom of Aidhne.

The Christian missionary, Grellan, established a church at Cill Cluaine (near present-day Ballinasloe) in Magh Seincheineoil. Cían is said to have "waited on the saint at the place."

In this time the kingdom was invaded by a branch of the Airgíalla, led by Eochaidh Ferdaghiall, his son Maine Mór and grandsons Amhalgaidh and Breasal mac Maine Mór. According to Leabhar Ua Maine:

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