Lake Hillier is a saline lake on the edge of Middle Island, the largest of the islands and islets that make up the Recherche Archipelago off the south coast of Western Australia. It is particularly notable for its pink color. A long and thin shore divides the Southern Ocean from the lake.
It is about 600 meters (2,000 ft) in length by about 250 meters (820 ft) in width. The lake is surrounded by a rim of sand and a dense woodland of paperbark and eucalyptus trees with a narrow strip of sand dunes covered by vegetation separating its northern edge from the northern coast of Middle Island. The most notable feature of the lake is its pink color. The vibrant color is permanent, and does not alter when the water is taken in a container. The source of the pink color is considered to be due to the presence of the organism Dunaliella salina. Air is the best mode of transportation for viewing the lake.