Fort Petrie was a World War II era fortification in Nova Scotia which played an important part in the Battle of the Atlantic and in protecting North Atlantic shipping ways. Today, several parts of Fort Petrie are still there, including its observation tower, subterranean fortifications, gun placements and other buildings.

Built in 1939 at a time when the threat of German invasion was high, it was vital in defending Sydney Harbour. It was decommissioned in 1956.