Neebish Island is located in the U.S. state of Michigan, in the St. Marys River, which connects Lake Superior and Lake Huron at the easternmost point of Michigan's upper peninsula. Located west of the international border that separates the United States from the Canadian province of Ontario, the island is within the Great Lakes-St. Lawrence seaway. Ship traffic heading up to Lake Superior pass on the island's east side, while downriver traffic to Lake Huron passes through a deepened channel on the island's west side.