Cellach Tosach mac Donngaile (died 809) was a king of the Uí Cheinnselaig of South Leinster.
He belonged to the Sil Chormaic sept of this branch of the Laigin and specifically to a branch which took over leadership of the Uí Dróna -the baronies of Idrone in modern County Carlow.
In 809 civil strife broke out among the Uí Cheinnselaig and Cellach was slain.
[2] He is called king of Ráith Étain (near Leighlinbridge, County Carlow), the seat of his sept.
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