Eochaid, son of Rhun

Eochaid ab Rhun (fl. 853-889) was a ninth century King of Strathclyde, who may have also been King of the Picts. He was a son of Rhun ab Arthgal, King of Strathclyde, and descended from a long line of British kings. Eochaid's mother is recorded to have been a daughter of Cináed mac Ailpín, King of the Picts. This maternal descent from the royal Alpínid dynasty may well account for the record of Eochaid reigning over the Pictish realm after the death of Cináed's son, Áed, in 878. According to various sources, Áed was slain by Giric, whose ancestry is uncertain and who then proceeded to usurp the Alban throne. Eochaid was posthumously given the epithet "In Tuilti" by the Prophecy of Saint Berchán.

Heir to the Brythonic kingdom of Strathclyde and a claimant to the Gaelic throne of the Picts, Eochaid was of mixed blood. Indeed, the name Eochaid is Gaelic and may indicate his maternal descent from the Alpínid dynasty. It is uncertain if Eochaid and Giric were relatives, unrelated allies, or even rivals. Whilst it is possible that they held the Pictish kingship concurrently as allies, it is also conceivable that they ruled successively as opponents. Another possibility is that, whilst Giric reigned as King of the Picts, Eochaid reigned as King of Strathclyde. Eochaid's floruit dates about the time when the Kingdom of Strathclyde seems to have expanded southwards into lands formerly possessed by the Kingdom of Northumbria. The catalyst for this extension of British influence appears to have been the Viking conquest of this northern English realm.