The Biscay Bay River is a stream located on the Avalon Peninsula of Newfoundland and Labrador, flowing into Trepassey Bay. It is one of six scheduled salmon rivers with drainage systems within the Avalon Wilderness Reserve, and also supports runs of seagoing brown trout, smelt, and brook trout, making it a destination primarily associated with angling rather than recreational paddling.

The Biscay Bay Trail, approximately 13 km in length, follows the river from Route 10 — roughly 10 km west of Portugal Cove South, near a Coast Guard communications tower — northward into the reserve, passing through an area known as the Backwaters toward Follies Pond, and continuing along the river to Cooks Pond near Stockes Pond. This trail corridor gives a sense of the river's general course and terrain. The Backwaters section in particular suggests low-lying, wet ground along the river's lower reaches.

Because the river lies within or adjacent to the Avalon Wilderness Reserve, paddlers should be aware that an entry permit is required from the Natural Areas Program, Land Management Division before entering the reserve. ATVs and snowmobiles are prohibited within the reserve. Anglers fishing for salmon also require a valid salmon licence in addition to the entry permit.

General canoe access into the Avalon Wilderness Reserve is noted from locations on Peak Pond Road, off the Salmonier Line (Route 90), though paddlers should consult topographical maps when planning a route. The terrain along the Biscay Bay Trail is wet enough that waterproof footwear is considered essential, which suggests paddlers should anticipate challenging portage conditions if required.