Strait of Canso, also Gut of Canso, channel in southeastern Canada, separating Cape Breton Island from the mainland of Nova Scotia. It is 23 km (15 mi) long and up to about 3.2 km (about 2 mi) wide, and links Saint Georges Bay, an arm of the Gulf of St. Lawrence, and Chedabucto Bay, an arm of the North Atlantic Ocean. The Canso Causeway, which opened in 1955, carries automobile and rail traffic across the strait. A canal and lock at the eastern end of the causeway enable large vessels to navigate the channel.