Cellach of Killala was a mid-6th-century Irish bishop associated with the Uí Fiachrach. According to the pseudo-historical text *Betha Chellaig*, he was the firstborn son of Eogan Bel, the King of Connacht. After being trained as a monk by Ciarán of Clonmacnoise, he eventually succeeded his father as ruler. His life is characterized by a complicated relationship with his mentor, who reportedly placed a curse upon him, and his eventual service as the bishop of Killala.