The Georgia Depression is a landform in the Pacific Northwest, part of the Insular Mountain System of the North American Cordillera in British Columbia, Canada, and in Washington, United States. It includes the Fraser Lowland, roughly equivalent to the region known as the Lower Mainland, and the Nanaimo Lowland and Nahwitti Lowland on Vancouver Island, as well as the Discovery Islands, an archipelago of many low-lying islands between them in the Johnstone Strait and adjoining waterways between the mainland and Vancouver Island. Farther north in the Coastal Trough is the Hecate Depression, which underlies Hecate Strait, Queen Charlotte Sound, Queen Charlotte Strait, and the Dixon Entrance. North of depression is the Alexander Archipelago, and to its east it is flanked by the Coast Mountains and the Washington portion of the Cascade Range. To its west are the Queen Charlotte Islands, including the Queen Charlotte Mountains and Nahwitti Depression, and the Vancouver Island Ranges and the Olympic Mountains in Washington Strait. The Trough includes the Puget Lowland (see Puget Sound basin).