The N78 road is a national secondary road in Ireland. The 50-kilometer-long (31 mi) road links the N77 national secondary road north of Kilkenny, County Kilkenny to the M9 national primary route at Mullamast in County Kildare. En route it passes through the towns of Castlecomer in County Kilkenny, Ballylynan in County Laois, and Athy in County Kildare. It is single carriageway throughout.