The main protagonist of The Táin, Cúchulainn, also known as Sétanta, is an archetypal hero. His hero’s journey is at the center of the narrative, and he is the most powerful warrior in Ireland. Cúchulainn is the 17-year-old nephew of Conchobor the king, the son of Sualdam mac Roich and Deichtine, and he is married to Emer. Like a demi-god, Cúchulain possesses some supernatural powers and is visited by others from the síde, which sets him apart from other men.

As a child, Cúchulainn trains with Scáthach to master many extraordinary feats, and his formation prepares him to singlehandedly defend Ulster against the incursion of the Irish armies. He is primarily motivated by his honor and community ties to Ulster, and the narrative continually tests his capabilities and moral limits through each single combat. For his young age, he is extremely brave and talented, but he often seeks to avoid conflict whenever possible; he takes the role of defender rather than aggressor. In tales of his childhood Cúchulainn is a chaotic, aggressive boy with a precocious talent for combat, but as an adult these talents are tempered and controlled, even in the face of provocation.