Milbanke Sound is a sound on the coast of the Canadian province of British Columbia, extending east from Queen Charlotte Sound, with Price Island on the west, Swindle Island on the north, and the Bardswell Group of islands on the south. Milbanke Sound is one of the open sea portions of the Inside Passage, with Seaforth Channel joining from the east and Finlayson Channel from the north. Mathieson Channel also connects to Milbanke Sound from the north, and leads to Fiordland Recreation Area.
The Heiltsuk peoples traditionally occupied the land around Milbanke Sound.
In late June, 1788, the British fur trader Charles Duncan, captain of the Princess Royal entered Milbanke Sound, which was then uncharted waters. He spent a few days trading with the Heiltsuk.
In the early 19th century the Hudson's Bay Company established Fort McLoughlin in the Milbanke Sound area. William Fraser Tolmie was stationed there in 1833-1834. Tolmie wrote about the fur trade in the area, saying that it was conducted with the Coast Tsimshians and Heiltsuks, using a pidgin jargon composed of the Kaigani and Tshatshinni dialects of Haida and English. Chinook Jargon, commonly used elsewhere, was not widely known in Milbanke Sound at the time.
In recent times archaeological investigations have been carried out in the Milbanke Sound area.