Quadra Island is an island off the eastern coast of Vancouver Island, British Columbia, Canada, part of the Discovery Islands. It is separated from Vancouver Island by Discovery Passage, and from Cortes Island by Sutil Channel. There are two small business centres on the island, one near the Vancouver Island BC Ferry terminal at Quathiaski Cove, and one near the Cortes Island ferry terminal at Heriot Bay. The island has many beaches, trails, lakes, and parks. Main Lake Provincial Park is located on the northern part of the island, and Rebecca Spit Marine Provincial Park is on the eastern shore, near Heriot Bay.