Kilmacthomas or Kilmactomas, often referred to locally as "Kilmac", is a town on the River Mahon in County Waterford, Ireland. It lies on the R677, a road north of the N25 national primary road from Dungarvan to Waterford.

The N25 road is a national primary road in Ireland, forming the route from Cork to Rosslare Europort via Waterford City. The road is part of the E30 European route and a short section is also part of the E01 European route. It forms part of the proposed Atlantic Corridor route.