The R665 road is a regional road in Ireland. The route runs from Mitchelstown to Clonmel via Ballyporeen, Clogheen and Ardfinnan, passing through parts of counties Cork, Tipperary and Waterford. The R665 was once a key part of the historic route from Dublin to Cork and was mapped as such as late as 1778. A turnpike road, it was also a key part of the route linking Mallow with Dublin, via today's N73.