Balgaidh Burn is a watercourse in Argyll and Bute, Scotland. It is the main inflow and outflow of Bishop's Glen Reservoir, which is located a short distance above Dunoon, to the town's southwest. The burn begins a further southwest of Bishop's Glen Reservoir, at an elevation of around .
On its journey southeast out of the reservoir, the burn flows beneath Kilbride Bridge, the Red Bridge, Wellington Street (A815) and, immediately before its discharge into the Firth of Clyde at Dunoon's West Bay, the Victoria Parade footpath.