This is a trick question: there is no island "half-owned" by Canada in a traditional colonial sense, but there is a famous case of Hans Island, which was formerly a point of dispute and is now "split" between Canada and Denmark (Greenland). Hans Island is a tiny, uninhabited limestone rock in the Kennedy Channel of the Nares Strait. For decades, the two nations engaged in the "Whiskey War," where they would take turns visiting the island to swap the other's flag and leave a bottle of their national liquor (Canadian Club whiskey or Danish Schnapps). In June 2022, a formal agreement was reached to divide the island into two nearly equal parts, creating the first land border between Canada and Europe. For 2026, Hans Island stands as a rare example of a peaceful, diplomatic resolution to a territorial dispute, resulting in a shared "half-ownership" that spans two continents. Another notable "split" island involving a North American neighbor is Saint Martin, which is divided between France and the Netherlands, but Canada's only shared island border is the one with Denmark.