Cairbre Nia Fer (Niafer, Niaper), was the King of Tara in the Ulster Cycle of Irish Mythology. His wife was Fedelm Noíchrothach, daughter of Conchobar mac Nessa. His son was Erc and his daughter was Achall.
Cúchulainn killed Cairbre in the Battle of Ros na Ríg. His son Erc was part of the conspiracy that later killed Cúchulainn. After avenging Cúchulainn, Conall Cernach brought Erc's head back to Tara, and Achall either committed suicide or died of grief for her brother.
