Basilaki Island (Moresby Island) is an island in the Louisiade Archipelago in Milne Bay Province, Papua New Guinea. It is located at the eastern end of the New Guinea mainland.

First recorded sighting by Europeans was by the Spanish expedition of Luís Vaez de Torres on 18 July 1606, that charted it as San Buenaventura (after Saint Bonaventure).

A party of French naturalists was believed to have been murdered in James Bay in October 1880.

This island was the scene of the murder of two sailors by natives in Hoopiron Bay, July 28, 1885. The men were Captain John Friar and John Watkins, a carpenter of Lallah Rook, a schooner registered in Saint John, New Brunswick. The vessel anchored in the bay to take on fresh water. After the murders, the crew sailed away.

The murders were revenge taken for two unpaid-for deaths of natives in Friar's employ. Despite a two-day search of the island on October 16, by the crews of Governor Blackall, and HMS Diamond and HMS Raven, the murderers were not found, although the skulls of Friar and the carpenter were recovered and given a burial at sea. Later Diamond returned and burned all the villages nearby.

Three planes were ditched off the island in 1943, a P-38H Lightning, a P-38F Lightning, and a B-24D Liberator "The Leila Belle".

The island is part of the following Wards:

All Wards belong to Bwanabwana Rural Local Level Government Area LLG, Samarai-Murua District, which are in Milne Bay Province.