Mnjikaning Fish Weirs, Native American fishing structure in Atherley Narrows, Canada.

The Mnjikaning Fish Weirs are an archaeological site at Atherley Narrows in Ontario, Canada, made up of submerged wooden stakes arranged across the narrow channel connecting Lake Couchiching and Lake Simcoe. The stakes were placed to funnel fish into shallower areas where they could be caught more easily.

These fish traps were first built around 4500 years ago, making them among the oldest known fishing structures in North America. They were repaired and rebuilt over time, which shows the site was actively used across many generations.

The weirs were historically called ouentaronk in Huron and tkaronto in Mohawk; the name tkaronto is believed to have passed through a series of transfers to become the name of Toronto. The site is managed by the Rama First Nation, which created the Mnjikaning Fish Fence Circle to protect and promote it.

A path from Bridge Street leads under the Highway 12 bridge to a viewing platform where the submerged stakes can be seen. Calm water and good light make the structures easier to spot, so early morning visits often give the clearest view.

The weirs were historically called ouentaronk in Huron and tkaronto in Mohawk; the name Toronto is believed to derive from these terms through a series of transfers, first to the route from Lake Ontario to the weirs, then to the fort at its end, and finally to the settlement near the fort.