The Mattock River is a river in Ireland that flows through County Louth and County Meath before joining the River Boyne. Starting near Collon, it meanders southeast, forming the boundary between the two counties at Coolfore. It then winds its way through Monknewtown and Dowth before finally merging with the River Boyne at Oldbridge. With an elevation of around 10 meters above sea level, this river offers a scenic route for those exploring the Irish countryside.