Cathcan of Rath Derthaighe

Saint Cathcan of Rath Derthaighe is an Irish saint of the undivided Church, remembered in the old martyrologies of Ireland as a bishop.

The Martyrology of Donegal, compiled in 1630 from older sources, commemorates him on 20 March. The Martyrology of Tallaght, from the early ninth century, lists a similar name on the same day. The date is that of the old Irish calendar, that is, in the old style.

Nothing else about him is preserved in the sources consulted.