Iago ab Idwal was a King of Gwynedd (reigned 950–979) and possibly Powys.
Iago was the son of the earlier King Idwal Foel but, upon Idwal's death in combat in 942, his uncle Hywel Dda invaded Gwynedd and seized the throne.
On Hywel's death in 950, Iago and his brother Ieuaf were able to drive out their cousins at the Battle of Carno and reclaim the kingdom.
The southern princes were finally defeated at the Battle of Llanrwst and chased back to Ceredigion.
Iago took Ieuaf prisoner in 969 and ruled another decade, with a brief hiatus in 974,[why?]