The Athboy-Tremblestown River is a 22-mile watercourse flowing southeast across County Meath, passing through the town of Athboy before joining the River Boyne approximately two miles upstream of Trim. The river flows through a catchment characterized by peatland and flat agricultural habitats with some hilly terrain. It features high banks, making chest waders essential for effective fishing. The fishery holds a good stock of wild brown trout, with the most productive fishing typically found from Athboy downstream to the Boyne confluence.