Bougainville Strait separates Choiseul Island, part of the Solomon Islands from Bougainville Island, the next to the northward and part of Papua New Guinea. The first European to pass through the strait was Louis Antoine de Bougainville in 1768, whose name was given to this water pathway. Lieutenant John Shortland of the Royal Navy sailed through the strait in 1788, giving the name of Treasury Islands to the numerous islands, lying in the strait. He named the strait after himself, but it later became known as Bougainville.