Tnúthgal mac Donngaile (or Tnúthgal mac Donngusa) (died 820) was a supposed King of Munster from the Eóganacht Chaisil branch of the Eoganachta.
He was a fifth generation descendant of Colgú mac Faílbe Flaind (died 678), a previous king.
He is not mentioned in the Irish annals and his death date of 820 is based on the accession of Feidlimid mac Cremthanin (died 847) in that year.
A confusion between him and Tnúthgal mac Artrach (died circa 807) may have occurred.
This biography of a member of an Irish royal house is a stub.