The Ballynahinch River is a small watercourse located in the Newry Mourne & Down council area of Northern Ireland, flowing near the town of Ballynahinch. The managed stretch covers approximately 2 kilometres. Paddlers should be aware that boats are not permitted on this river, making it unsuitable for kayaking or canoeing. Even setting aside this restriction, the river has been characterised as small and not well-suited to paddling.

The Ballynahinch River forms the upper headwaters of a longer river system, eventually transitioning into the Annacloy River and then the Quoile, which flows through Downpatrick to the Quoile Barrage and into Strangford Lough. Those sections downstream offer more viable paddling options — the Annacloy River in particular is noted for white water paddling between Mason's Bridge and Kilmore, while the stretch from Kilmore to Annacloy is mostly flat water with a few weirs. The Quoile itself, from Annacloy to the Barrage, is entirely flat water.

There is no car parking onsite at the Ballynahinch River. The river is primarily managed as a game fishery by DAERA, with brown trout fishing available downstream from Kilmore. The fishing season runs from 1st March to 31st October. Paddlers looking for accessible water in this part of Northern Ireland should look to the downstream sections of the river system rather than the Ballynahinch River itself.