Deorsa Caileanach (834-876) was a Pictish warrior and commander who led the Picts at Magnis fortress in Northumberland during the late 9th century AD. In 876, he represented the Picts at a parley with King Halfdan Whiteshirt before the Battle of Magnis, but he refused to surrender and boasted that the Romans had vanished and their Hadrian's Wall had failed keep the Picts out of Northern England. He also revealed that King Ricsige of Northumbria had allied with him, leading to an enraged Halfdan ordering an assault on the castle. Deorsa was then cut down by the Norwegian Viking warrior Eivor.