Located at 5°38′30″S 155°52′40″W / 5.64167°S 155.87778°W / -5.64167; -155.87778Coordinates: 5°38′30″S 155°52′40″W / 5.64167°S 155.87778°W / -5.64167; -155.87778, and measuring 8.9 kilometres (5.5 miles) east-to-west and 3.5 kilometres (2.2 miles) north-to-south, Starbuck Island has a land area of 1,620 hectares (4,003 acres). It is a low, dry, coral limestone island with a steep beach backed by a 6–8-metre-high (20–26 ft) bank composed of large coral fragments. Several hypersaline lagoons form on the island's eastern side. These occasionally dry up, and are said to be dangerous to approach: one worker during the island's guano-mining days sank up to his neck in salty mud before being rescued.
There is no freshwater on the island, which is one of the drier atolls in the Line Island group. Annual yearly rainfall averages approximately 800 mm (31.5 in).
Little vegetation exists on Starbuck; stunted Sida fallax scrub and low herbs and grasses predominate, with a few Cordia subcordata bushes and bunch grass rounding out the flora. Recent photos showed a few palm trees growing near the center of the island.
The island boasts a large colony of sooty terns, estimated at 1.5 million pairs, together with Polynesian rats, feral cats, green turtles, and around fifteen other species of seabirds. Other accounts estimate the sooty tern population to be as high as three to six million birds.
The island was noted for the unbearable screaming of seabirds, extreme heat and blinding sunlight.
Starbuck Island was first sighted in 1823 by Valentine Starbuck, American-born master of the British whaling ship L'Aigle on which the young king and queen of Hawaii, travelled to England in 1823–1824. However it had probably been sighted previously that same year by his cousin and fellow-whaler Capt. Obed Starbuck. Starbuck Island was charted in 1825 by Captain The 7th Lord Byron (a cousin of the famous poet). Byron, commanding the British warship HMS Blonde, was returning to London from a special mission to Honolulu to repatriate the remains of the Hawaiian royal couple, King Kamehameha II and Queen Kamāmalu who had died of measles while trying to visit King George IV. Lord Byron discovered and charted Malden Island, which he named after his surveying officer, Mauke, and Starbuck Island.
It was claimed by the United States under the 1856 Guano Act, but controlled by Britain after 1866, when possession was taken by Commodore Swinburn of HMS Mutine. Starbuck Island was mined for phosphate between 1870 and 1893. Because of its low profile (at its highest point, the island rises to about 5 meters) and the dangerous surrounding reefs, a number of ships were wrecked at Starbuck Island in the late 19th century, including the French transport Euryale on March 10, 1870. The captain of this ship, the future contre-admiral Albert Des Portes, who stayed 35 days with his crew on the atoll before being rescued and coming back to France with all the members, finally found the right geographical location of the island. On August 7, 1896 the Norwegian ship "Seladon" was wrecked against the barrier. The crew went into the lifeboats and drifted for 30 days until they landed on the island of Niulakita, Tuvalu. For 10 months they lived together with a few natives until they were picked up by a ship and rescued.
The island formed a part of the British Gilbert and Ellice Islands Colony prior to the independence of Kiribati in 1979. American claims to the atoll were formally vacated in the Treaty of Tarawa, signed that same year.
Starbuck Island has been designated as the Starbuck Island Wildlife Sanctuary. In 2014 the Kiribati government established a 12-nautical-mile fishing exclusion zone around each of the southern Line Islands: Caroline (commonly called Millennium), Flint, Vostok, Malden, and Starbuck.