Fort de l'Isle is a site in Alberta, Canada, containing the remains of three trading posts that existed from 1799 to some time before 1808.
From the time of Médard des Groseilliers it had been unclear whether Canadian jurisdiction extended beyond the Saint Lawrence basin.
Both posts were abandoned in favor of Fort Edmonton upstream or Paint Creek House/Fort Vermilion downstream.
The surviving visible remains consist of cellar depressions and piles of chimney rock.
The island can be reached only by boat or by snowshoes in winter; a fairly powerful outboard is needed because of the current.