The Strait of Georgia or the Georgia Strait is a strait between Vancouver Island, and the mainland coast of British Columbia, Canada and extreme northern Washington, United States. It is approximately 240 kilometres (150 mi) long and varies in width from 20 to 58 kilometres (12 to 36 mi). Along with the Strait of Juan de Fuca and Puget Sound, it is a constituent part of the Salish Sea. Archipelagos and narrow channels mark each end of the Strait of Georgia, the Gulf Islands and San Juan Islands in the south, and the Discovery Islands in the north. The main channels to the south are Haro Strait and Rosario Strait, which connect the Strait of Georgia to the Strait of Juan de Fuca. In the north, Discovery Passage is the main channel connecting the Strait of Georgia to Johnstone Strait. The strait is a major navigation channel on the west coast of North America, owing to the presence of the port of Vancouver, and also due to its role as the southern entrance to the infracoastal route known as the Inside Passage.
The United States Geological Survey defines the southern boundary of the Strait of Georgia as a line running from East Point on Saturna Island to Patos Island, Sucia Island, and Matia Island, then to Point Migley on Lummi Island. This line touches the northern edges of Rosario Strait, which leads south to the Strait of Juan de Fuca, and Boundary Pass, which leads south to Haro Strait and the Strait of Juan de Fuca.