Coordinates: 20°28′S 115°32′E / 20.46°S 115.54°E
The Montebello Islands, also known as the Monte Bello Islands, are an archipelago of around 174 small islands (about 92 of which are named) lying 20 kilometres (12 mi) north of Barrow Island and 130 kilometres (81 mi) off the Pilbara coast of north-western Australia. Montebello is Italian for "beautiful mountain". The islands form a conservation park administered by the Western Australian Department of Environment and Conservation, and it is likely that the shallow waters around them will become a marine conservation reserve. The islands were the site of three nuclear weapons tests by the British military in the 1950s.
The islands of the archipelago have a collective land area of about 22 km2. The largest islands, Hermite (or Hermit) and Trimouille have areas of 1022 ha and 522 ha respectively. They consist of limestone rock and sand. The rocky parts are dominated by Triodia hummock grassland with scattered shrubs, while the sandy areas support grasses, sedges and shrubs, mainly Acacia. Patches of mangroves grow in sheltered bays and channels of the archipelago, especially at Hermite Island. The climate is hot and arid with an annual average rainfall of about 320 mm.