Kingdom of Dál Riata

Dál Riata, also known as Dalriada, was a Gaelic kingdom that encompassed the western seaboard of Scotland and northeastern Ireland, straddling the North Channel. At its height in the 6th and 7th centuries, Dál Riata covered what is now Argyll in Scotland and part of County Antrim in Northern Ireland. The kingdom eventually became associated with the Gaelic Kingdom of Alba.

In Argyll, Dál Riata consisted of four main kindreds or tribes, each with its own chief:

• The Cenél nGabráin, based in Kintyre.
• The Cenél nÓengusa, based on Islay.
• The Cenél Loairn, who gave their name to the district of Lorn.
• The Cenél Comgaill, who gave their name to Cowal.

The hillfort of Dunadd is believed to have been its capital, with other royal forts including Dunollie, Dunaverty, and Dunseverick. The kingdom included the important monastery of Iona, a center of learning and a key player in the spread of Celtic Christianity throughout northern Britain.

Dál Riata had a strong seafaring culture and a substantial naval fleet. The kingdom is said to have been founded by the legendary king Fergus Mór (Fergus the Great) in the 5th century. It reached its peak under Áedán mac Gabráin (r. 574–608), who expanded its influence through naval expeditions to Orkney and the Isle of Man, and military assaults on Strathclyde and Bernicia. However, Dál Riata's expansion was checked by King Æthelfrith of Bernicia at the Battle of Degsastan in 603.

The reign of Domnall Brecc (died 642) saw serious defeats in both Ireland and Scotland, ending Dál Riata's "golden age" and reducing it to a client kingdom of Northumbria. In the 730s, the Pictish king Óengus I led campaigns against Dál Riata, bringing it under Pictish overlordship by 741. The kingdom experienced a decline and faced intermittent Viking raids from 795 onwards.

The late 8th century saw differing scholarly interpretations of Dál Riata's fate. Some argue that the kingdom saw no revival after a long period of domination (c. 637 to c. 750–760), while others see a resurgence under Áed Find (736–778) and claim that Dál Riata may have usurped the kingship of Fortriu. By the mid-9th century, there may have been a merger of the Dál Riatan and Pictish crowns, with some sources suggesting that Cináed mac Ailpín (Kenneth MacAlpin) was king of Dál Riata before becoming king of the Picts in 843, following a major Viking defeat of the Picts.

Latin sources often referred to the inhabitants of Dál Riata as Scots (Scoti), a term initially used by Roman and Greek writers for the Irish Gaels who raided and colonized Roman Britain. Later, it referred to Gaels from both Ireland and elsewhere. Herein, they are referred to as Gaels or Dál Riatans. The kingdom's independence ended as it merged with Pictland to form the Kingdom of Alba, marking the genesis of what would become Scotland.