Miscou Island (French: Île Miscou) is a Canadian island in the Gulf of St. Lawrence at the northeastern tip of Gloucester County, New Brunswick.

It is separated from neighbouring Lamèque Island to the southwest by the Miscou Channel with both islands forming Miscou Harbour. Lamèque Island and Miscou Island separate Chaleur Bay from the Gulf of Saint Lawrence.

Miscou Island is from the Mi'kmaq 'Susqu,' meaning "low land" or "boggy marsh". "It forms an admirable descriptive name, for the most striking fact about the physical geography of Miscou is the prevalence of open bogs..." (Ganong)

The Miscou Channel is bridged between the community of Little Shippegan on Lamèque Island to the community of Miscou Harbour on Miscou Island by the Miscou Island Bridge which opened in 1996, replacing a cable ferry and physically connecting Route 113.

The island formed its own local service district from 1980 until the end of 2022; it now comprises the Acadian Peninsula rural district.

The Miscou Island area was one of the first areas explored by Jacques Cartier in 1534 and was a fishing base for Basque fishermen in the same period. A Jesuit mission was established at Miscou Harbour in 1634. It was an important, although seasonal, port of commerce in its early years of European exploration of Canada.

Natives were allegedly frightened to go to the island due to the legendary GouGou monster which inhabited Miscou and which they feared. Despite this native hunters annually overcame their fear of the monster to set up seasonal camps on the island.

The first permanent settler was John Campbell who emigrated from Scotland and moved there around 1817. Soon after came Robert Harper, John Marks, Thomas Cowan and Andrew Wilson; the first 3 married Campbell's daughters. They were followed by fishermen from the Channel Islands of Jersey and Guernsey who processed codfish at the Northern tip of the island to ship back to Europe and Acadians who settled on more arable lands in the interior.