Navy Island was a small island situated within the Inner Harbour of Saint John, New Brunswick in Canada. For centuries, Navy Island existed as a narrow, oval shaped hunk of rock sitting roughly at the turning point of the harbour where the deep open water ends and the harbour approaches the Reversing Falls. However, the island ceased to exist in its traditional form when the construction of the Saint John Harbour Bridge linked the island to the mainland in the 1970s. The island now sits under the western footing of the bridge, and is survived in name by the Navy Island Forest Products Terminal, operated by the Port of Saint John.
The island is noted as the location of the so-called Navy Island Gold, a storied treasure supposedly left behind by privateers or smugglers who were members of the Royal Kennebecasis Adventurers Society. Despite great effort and expense, no treasure has been found, and skeptics have dismissed it as a sinkhole and natural cavities. Following the construction of the Harbour Bridge in the 1970s, much of the surface area of the island was heavily altered and developed, leading many to believe that if any treasure had existed, it would be nearly impossible to ever recover.