In Irish mythology, Mac Cecht of the Tuatha Dé Danann was a son of Cermait, son of the Dagda.

He and his brothers Mac Cuill and Mac Gréine killed Lug in revenge for their father. The three brothers became joint High Kings of Ireland, rotating the sovereigty between them a year at a time, covering twenty-nine or thirty years depending on the source consulted. They were the last kings of the Tuatha Dé Danann before the coming of the Milesians.

Mac Cecht's given name was Téthur. He was named Mac Cecht after his god, Cecht, the ploughshare. His wife was Fodla.