Dál Riata (also Dalriada or Dalriata) is a Gaelic overkingdom on the western coast of Scotland (tat this time Pict-land) and part of Ulster.

In the late 6th and early 7th century it encompasses roughly what is now Argyll and Bute and Lochaber in Scotland and also County Antrim in Northern Ireland.

In Argyll it consists initially of three kindreds: Cenél Loairn (kindred of Loarn) in north and mid-Argyll, Cenél nÓengusa (kindred of Óengus) based on Islay and Cenél nGabráin (kindred of Gabrán) based in Kintyre; a fourth kindred, Cenél Chonchride in Islay, is seemingly too small to be deemed a major division.

By the end of the 7th century another kindred, Cenél Comgaill (kindred of Comgall), has emerged, based in eastern Argyll.

The Lorn and Cowal districts of Argyll take their names from Cenél Loairn and Cenél Comgaill respectively, while the Morvern district was formerly known as Kinelvadon, from the Cenél Báetáin, a subdivision of the Cenél Loairn Dál Riata is commonly seen as having been a Gaelic Irish colony in Scotland founded by Irish colonists who brought with them Christianity; writing; and new technologies, which were not inherent in Pictland.

Some archeologists, like Ewan Campbell, have argued against the idea that Dál Riata was an Irish colony.

The inhabitants of Dál Riata are often referred to as Scots (Latin Scoti), a name that in earlier times had been used only for the inhabitants of Ireland; its original meaning is uncertain but it later refers to Gaelic-speakers, whether from Ireland or elsewhere.

They are referred to here as Gaels, an unambiguous term, or as Dál Riatans.

The kingdom reaches its height under Áedán mac Gabráin (r. 574-608), but its growth is checked at the Battle of Degsastan in 603 by Æthelfrith of Northumbria.

Serious defeats in Ireland and Scotland in the time of Domnall Brecc (d. 642) end Dál Riata's "golden age", and the kingdom becomes a client of Northumbria, at this time subject to the Picts.

There is disagreement over the fate of the kingdom from the late eighth century onwards.

Some scholars have seen no revival of Dál Riata after the long period of foreign domination (after 637 to around 750 or 760), while others have seen a revival of Dál Riata under Áed Find (736–778), and later Kenneth MacAlpin (Cináed mac Ailpín, who is claimed in some sources to have taken the kingship there in c.840 following the disastrous defeat of the Pictish army by the Danes): some even claim that the kingship of Fortriu was usurped by the Dál Riata several generations before MacAlpin (800–858).

The kingdom's independence ends in the Viking Age, as it merges with the lands of the Picts to form the Kingdom of Alba.The name of the kingdom is preserved in the etymology of the Dalradian geological series, a term coined by Archibald Geikie because its outcrop has a similar geographical reach to that of the former Dál Riata.