Dumnagual III (Welsh: Dyfnwal ap Tewdwr, died c. 760) was a king of Strathclyde in the mid-eighth century (probably 754–760).
The same source indicates that on August 1, 756, they arrived at Alt Clut (Dumbarton Rock, Dumnagual's capital) and obtained the homage of the Britons.
However, nine days later, the Northumbrian king's army was destroyed while Eadberht was leading it between "Ouania" and "Niwanbirig",[2] probably meaning "Govan" and "Anglian Northumbria".
[3] Dumnagual is usually regarded as the king of Alt Clut in the period, but it has also been suggested that the destroyer of the Northumbrian army was Óengus.
[4] Phillimore's reconstruction of the Annales Cambriae puts Dumnagual's death in battle at 760.