Cathal mac Dúnlainge (died 819) was a king of the Uí Cheinnselaig of South Leinster.
He was of the Sil Máeluidir sept of this branch of the Laigin, who were found in the later baronies of Shelmalier on the lower reaches of the Slaney River in southern modern County Wexford.
Cathal acquired the throne after the death of his predecessor Cellach Tosach mac Donngaile of the Uí Dróna in 809.
In 817 he led forces which included men from the monastery of Tech Munnu (Taghmon) in an attack on the community of Ferns where 400 were slain by him.
[4] At his death obit in 819 he is styled King of the Uí Cheinnselaig and prior or vice abbot of Ferns[5]