The Lombok Strait (Indonesian: Selat Lombok), is a strait connecting the Java Sea to the Indian Ocean, and is located between the islands of Bali and Lombok in Indonesia. The Gili Islands are on the Lombok side.
Its narrowest point is at its southern opening, with a width of about 20 km between the islands of Lombok and Nusa Penida, in the middle of the strait. At the northern opening, it is 40 km across. Its total length is about 60 km. Because it is 250 m deep — much deeper than the Strait of Malacca — ships that draw too much water to pass through Malacca (so-called "post Malaccamax" vessels) often use the Lombok Strait, instead.
The Lombok Strait is notable as one of the main passages for the Indonesian Throughflow that exchanges water between the Indian Ocean and the Pacific Ocean.
It is also part of the biogeographical boundary between the fauna of Indomalaya ecozone and the distinctly different fauna of Australasia. The boundary is known as the Wallace Line, for Alfred Russel Wallace, who first remarked upon the striking difference between animals of Indo-Malaysia from those of Australasia and how abrupt the boundary was between the two biomes.
West Nusa Tenggara (Indonesian: Nusa Tenggara Barat) is a province of Indonesia. It comprises the western portion of the Lesser Sunda Islands, with the exception of Bali which is its own province. Mataram, on Lombok, is the capital and largest city of the province. The 2010 census recorded the population at 4,496,855. The two largest islands in the province are Lombok in the west and the larger Sumbawa island in the east.