Gros Cap Reefs Light, Navigation lighthouse at entrance of St. Mary's River, Sault Ste. Marie, Canada.

Gros Cap Reefs Light is a lighthouse at the entrance of the St. Mary's River in Sault Ste. Marie, Canada. The concrete tower includes a three-story keeper's dwelling and a skeletal mast framework painted with red trim.

A lightship marked the Gros Cap Reef from 1923 until the permanent lighthouse was completed in 1953 at the entrance to St. Mary's River from Whitefish Bay. The new aid to navigation made the Point Iroquois Light redundant, and it was deactivated in 1962. The Canadian Coast Guard owns the structure.

The light is owned by the Canadian Coast Guard and stands on the southwest edge of the Gros Cap Reef. Its opening in 1953 allowed the Point Iroquois Light to be deactivated in 1962, so the reef light took over that guiding role at the river entrance.

The beacon sends a red flash every 5 seconds and can be seen from ships up to 12 nautical miles away. A helicopter landing pad provides access for maintenance work.

The tower itself has been removed: what remains is a three-story base housing the keeper's quarters, with the light on a skeletal mast. A helipad serves the site, and a non-directional beacon for Sault Ste. Marie Airport approaches was decommissioned and its antenna taken down because of high maintenance costs.