Ballynahinch River is a river in County Down, Northern Ireland. The Ballynahinch River, flowing east through Ballynahinch, and the Carson's Dam River, flowing south through Crossgar, join at Kilmore, and the united stream is called the Annacloy River, and lower down the River Quoile, falling into the southwest angle of Strangford Lough near Downpatrick.