The Cruthin (Old Irish pronunciation: [ˈkɾˠʊθʲɪn̠ʲ]; Middle Irish: Cruithnig or Cruithni; Modern Irish: Cruithne [ˈkɾˠɪhn̠ʲə]) were a people of early medieval Ireland. Their heartland was in Ulster and included parts of the present-day counties of Antrim, Down and Londonderry. They are also said to have lived in parts of Leinster and Connacht. Their name is the Irish equivalent of Priteni, an ancient name for the Celtic Britons, and was sometimes used to refer to the Picts. However, there is a debate among scholars as to the relationship of the Cruthin with the Britons and Picts.
The Cruthin comprised a number of túatha (territories), which included the Dál nAraidi of County Antrim and the Uí Echach Cobo of County Down. Early sources distinguish between the Cruthin and the Ulaid, who gave their name to the over-kingdom, although the Dál nAraidi would later claim in their genealogies to be na fír Ulaid, "the true Ulaid". The Loígis, who gave their name to County Laois in Leinster, and the Sogain of Leinster and Connacht, are also claimed as Cruthin in early Irish genealogies.
By 773 AD, the annals stopped using the term Cruithne in favour of the term Dál nAraidi, who had secured their over-kingship of the Cruthin.
In medieval Irish writings, the name is variously spelt Cruthin, Cruithin, Cruthini, Cruthni, Cruithni or Cruithini (Modern Irish: Cruithne). It is thought to relate to the Irish word cruth, meaning "form, figure, shape". The name is believed to derive from *Qritani, a Goidelic/Q-Celtic version of the Brittonic/P-Celtic *Pritani. Pytheas referred to the old P-Celtic name as 'Pretannia', which was later latinized as Britanni, the Roman name for the Celtic Britons.
The name Cruthin survives in the placenames Duncrun (Dún Cruithean, "fort of the Cruthin") and Drumcroon (Droim Cruithean, "ridge of the Cruthin") in County Londonderry, and Ballycrune (Bealach Cruithean, "pass of the Cruthin") and Crown Mound (Áth Cruithean, "ford of the Cruthin") in County Down. These placenames are believed to mark the edges of Cruthin territory.
Early Irish writers used the name Cruthin to refer to both the north-eastern Irish group and to the Picts of Scotland. Likewise, the Scottish Gaelic word for a Pict is Cruithen or Cruithneach, and for Pictland is Cruithentúath. It has thus been suggested that the Cruthin and Picts were the same people or were in some way linked. Professor T. F. O'Rahilly wrote that the Qritani/Pritani were "the earliest inhabitants of these islands to whom a name can be assigned". It has also been suggested[by whom?] that Cruthin was a name used to refer to all the Britons who were not conquered by the Romans – those who lived outside Roman Britain, north of Hadrian's Wall.
Other scholars disagree, pointing out that although Cruthin was used to translate Picti into Irish, Picti was never used to translate Cruthin into Latin. Professor Dáibhí Ó Cróinín says the "notion that the Cruthin were 'Irish Picts' and were closely connected with the Picts of Scotland is quite mistaken" while Professor Kenneth H. Jackson has said that the Cruthin "were not Picts, had no connection with the Picts, linguistic or otherwise, and are never called Picti by Irish writers". There is no archaeological evidence of a Pictish link and in archaeology the Cruthin are indistinguishable from their neighbours in Ireland. The records show that the Cruthin bore Irish names, spoke Irish and followed the Irish derbfine system of inheritance rather than the matrilineal system sometimes attributed to the Picts.
Dál Riata was a Gaelic kingdom that included parts of western Scotland and northeastern Ireland. The Irish part of the kingdom lay in the middle of Cruthin territory. Historian Alex Woolf has suggested that the Dál Riata were a part of the Cruthin, and that they were descended from the Epidii.
By the start of the historic period in Ireland in the 6th century, the over-kingdom of Ulaid was largely confined to east of the River Bann in north-eastern Ireland. The Cruthin however still held territory west of the Bann in County Londonderry, and their emergence may have concealed the dominance of earlier tribal groupings.
A certain Dubsloit of the Cruthin is said to have killed the son of the High King Diarmait mac Cerbaill in 555 or 558, and Diarmait himself was killed by a Cruthin over-king of Ulster, Áed Dub mac Suibni, in 565.
In 563, according to the Annals of Ulster, an apparent internal struggle amongst the Cruthin resulted in Báetán mac Cinn making a deal with the Northern Uí Néill, promising them the territories of Ard Eólairg (Magilligan peninsula) and the Lee, both west of the River Bann in County Londonderry. As a result, the battle of Móin Daire Lothair (modern-day Moneymore, County Londonderry) took place between them and an alliance of Cruthin kings, in which the Cruthin suffered a devastating defeat. Afterwards the Northern Uí Néill settled their Airgíalla allies in the Cruthin territory of Eilne, which lay between the River Bann and the River Bush. The defeated Cruthin alliance meanwhile consolidated itself within the Dál nAraidi dynasty.
Their most powerful historical king was Fiachnae mac Báetáin, King of Ulster and effective High King of Ireland. Under their king, Congal Cláen, they were routed by the Uí Néill at Dún Cethirnn (between Limavady and Coleraine) in 629, although Congal survived. The same year, the Cruthin king Mael Caích defeated Connad Cerr of the Dál Riata at Fid Eóin, but in 637 an alliance between Congal Cláen and Domnall Brecc of the Dál Riata was defeated, and Congal was killed, by Domnall mac Aedo of the northern Uí Néill at Mag Roth (Moira, County Down), establishing the supremacy of the Uí Neill in the north. In 681 another Dál nAraide king, Dúngal Eilni, and his allies were killed by the Uí Néill in what the annals call "the burning of the kings at Dún Cethirnn". The ethnic term "Cruthin" was by this stage giving way to the dynastic name of the Dál nAraide. The Annals record a battle between the Cruthin and the Ulaid at Belfast in 668, but the last use of the term is in 773, when the death of Flathruae mac Fiachrach, "rex Cruithne", is noted. By the twelfth century it had fallen into disuse as an ethnonym, and was remembered only as an alternative name for the Dál nAraide.
In modern times, some Unionist writers in Northern Ireland—in particular Ian Adamson—have seen the Cruthin as an ancient reflection of their own northern separatism and affinity with Britain. In his 1974 book Cruthin: The Ancient Kindred, Adamson argues that the Cruthin settled Ireland before the Gaels; that the two groups were at war for centuries, seeing the tales of the Ulster Cycle as representations of this; and that many of the Cruthin were driven to Scotland after their defeat in the battle of Moira (637), only for their descendants to return to Ireland in the 17th century Plantation of Ulster. Historians reject his interpretations, with some accusing him of creating a sectarian narrative in which Ulster Protestants have a prior to claim to Ireland. Adamson denies this, claiming his interpretation of history offers "the hope of uniting the Ulster people at last".