In Irish Mythology Cimbáeth or Cimbaoth was a High King of Ireland. He ruled in rotation with his cousins Áed Ruad and Díthorba, each ruling for seven years in turn. Each ruled for three seven-year periods.

Áed Ruad had died after his third stint as king, and when Cimbáeth's third period ended Áed's daughter Macha demanded the kingship in her father's place. Cimbáeth and Díthorba refused, but she defeated them on the battlefield, killing Díthorba in Connacht. She married Cimbáeth and ruled jointly with him for a further seven years. He died of plague at Emain Macha, and Macha became the only queen in her own right in the List of High Kings of Ireland.