Loingsech mac Óengusso

Loingsech mac Óengusso (died 703) was an Irish king who was High King of Ireland. Loingsech was a member of the northern Cenél Conaill branch of the Uí Néill. Although his father Óengus (died 650) had not been High King, his grandfather Domnall mac Áedo (died 642) had been.

Loingsech is first mentioned in the annals of Ireland under the year 672 when he defeated Dúngal mac Máele Tuil of the Cenél mBógaine who was slain. The Cenél mBógaine were a branch of the Cenél Conaill located in southwest County Donegal. The Annals of Ulster do not mention Loingsech as victor, whereas the Annals of Tigernach do. The Annals of the Four Masters refer to Loingsech as chief of the Cenél Conaill with regards to this event. His accession to lordship of the Cenél Conaill is not mentioned, however the death of his uncle Ailill Flann Esa (died 666) is recorded during the plague years.

The Chronicle of Ireland records the beginning of Loingsech's reign in 696, having recorded the killing of his predecessor Fínsnechta Fledach the year previously. The record in Annals of Ulster may show that Congalach mac Conaing Cuirre (died 696) of the Síl nÁedo Sláine branch of the southern Uí Néill was a candidate for the high kingship after the killing of Fínsnechta, in competition with Loingsech. It is not until after Congalach's death that the annal, probably based on a contemporaneous chronicle kept on Iona, announces the beginning of Loingsech's reign. The Annals of Tigernach on the other hand place the beginning of Loingsech's reign in 695 before the death of Congalach. He ruled as high king from 695–703.

It was in his reign that Adomnán – a member of the Cenél Conaill- came to preach in Ireland. Loingsech appears as the first non-ecclesiastical signatory of Adomnán's "law of the innocents"—the Cáin Adomnáin—agreed at the Synod of Birr in 697. Loingsech gave his full support to this law.

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