Bikini Atoll is an atoll, listed as a World Heritage Site, in the Micronesian Islands of the Pacific Ocean, part of Republic of the Marshall Islands. It consists of 23 islands surrounding a deep 229.4-square-mile (594.1 km2) central lagoon at the northern end of the Ralik Chain (approximately 87 kilometres (54 mi) northwest of Ailinginae Atoll and 850 kilometres (530 mi) northwest of Majuro), now universally significant to the world as follows: Within Bikini Atoll, Bikini Island is the northeastern most and largest islet, measuring 4 kilometres (2.5 mi) long. About twelve kilometres to the northwest is the islet of Aomen. As part of the Pacific Proving Grounds it was the site of more than 20 nuclear weapons tests between 1946 and 1958.
The first Westerner to see the atoll, in the mid-1820s, was the Russian captain and explorer Otto von Kotzebue, who named the atoll Eschscholtz Atoll after the Russian scientist Johann Friedrich von Eschscholtz. The atoll, however, has always been called Bikini by the native Marshall Islanders, from Marshallese "Pik" meaning "surface" and "Ni" meaning "coconut". The name was popularized in the United States not only by nuclear bomb tests, but because the bikini swimsuit was named after the island in 1946. The two-piece swimsuit was introduced within days of the first nuclear test on the atoll, when the name of the island was in the news. Introduced just weeks after the one-piece "Atome" was widely advertised as the "smallest bathing suit in the world", it was said that the bikini "split the atom".