Tigernach or Tiarnach of Clones (anglicised Tierney) was one of the pre-eminent saints of the territory ruled by the Uí Chremthainn dynasty, together with Mac Caírthinn of Clogher and Mo Laisse of Devenish.

The first foundation by Tigernach, in about the same area, is Gabáil-liúin, now Galloon Island, Upper Lough Erne (County Fermanagh), on the border of that kingdom.

[1] Tigernach's Life depicts an early stage when the Uí Chremthainn had not yet branched off but had a single royal seat near Clogher.

[4] Having heard his teacher prophesy the foundation of a prominent church, Tigernach went to Rome to obtain relics and returned to Brigit in Leinster, who urged him to become a bishop.

An angel appeared to him and following his directions, Tigernach sought out the boundary of the kingdom to make his first foundation, namely Galloon.

The ruins of a 12th-century abbey building can still be found in the town, along with a sarcophagus reputed to have been built to house Tigernach's remains, and a 9th-century round tower and high cross.