Lunn Island is a solitary island of Papua New Guinea in the Solomon Sea, belonging to the Louisiade Archipelago. It belongs to Milne Bay Province and is located between the Engineer Group, which is 8.3 km to the west, and the Torlesse Islands, which area 18.3 km to the east. The Deboyne Islands are another 22 km eastward.
Lunn Island is uninhabited, densely wooded and has a land area of 51 hectares. It is 1.14 km long and up to 550 meters wide.