Bikini Atoll (also known as Pikinni Atoll) is an atoll in one of the Micronesian Islands in the Pacific Ocean, part of Republic of the Marshall Islands. It consists of 23 islands surrounding a 229.4-square-mile (594.1 km2) lagoon. As part of the Pacific Proving Grounds it was the site of more than 20 nuclear weapons tests between 1946 and 1958.

The navigator and explorer Otto von Kotzebue named Bikini Atoll Eschscholtz Atoll after the scientist Johann Friedrich von Eschscholtz.

Preceding the nuclear tests, the indigenous population was relocated to Rongerik Atoll, though during the Castle Bravo shot in particular some members of the population were exposed to nuclear fallout