Smith Island is an island off of and north of the mouth of the Skeena River in the North Coast region of British Columbia, Canada. It is located just south of the City of Prince Rupert. On its southern tip is the former settlement of Oceanic. Tsum Tsadai Inlet is a narrow inlet on the north side of the island, with its opening to the west. Tsum Tsadai Rock is located at the inlet's opening to the sea. Dashken Indian Reserve No. 22 is on the east side of Smith Island, facing De Horsey Island which is to the east.
Marcus Passage is the name of the waters to the south of the island. To the north is Inverness Passage, separating Smith Island from the Tsimpsean Peninsula and named for one of the earliest cannery companies in the area which was located at the mouth of the Skeena. The eastern end of Inverness Passage, to the north of De Horsey Island, which is immediately southeast of Smith Island, and is the opening into it from the mouth of the Skeena, is Eleanor Passage. De Horsey Passage separates De Horsey Island from Smith Island on the latter's east side. Croasdaile Island is to the south of the southern tip of Smith Island.