Mantsinsaari Island (also Mantsi, Russian: Остров Мантсинсаари, Finnish: Mantsinsaari) is an island on the North-East of Lake Ladoga in the Salmi settlement in the Pitkyaranta municipality in the Republic of Karelia. The island is nearly uninhabited. Before World War II, the island was a part of the Salmi municipality in Finland, and it had 1,500 inhabitants. The island did not have a bridge, instead a cable ferry. The main sources of livelihood were cultivation and fishing.