Dionysius Ó Donnchadha was an Irish Roman Catholic bishop who served as the Bishop of Kilmacduagh from 1441 to 1478.
Nothing appears to be known of this bishop's term. A Diarmaid Ó Donnchadha became bishop of the same diocese in 1418.
References
Dionysius Ó Donnchadha Wikipedia(Text) CC BY-SA