比基尼环礁（英语：Bikini Atoll，亦作Pikinni Atoll），是一个属于马绍尔群岛的堡礁，由23个小岛环绕着一个面积达229.4平方英里（594.1 km）的潟湖组成。美国从1946年到1958年在马绍尔群岛共进行了20多次原子弹和氢弹的爆炸。2010年7月31日被列入世界文化遗产，是该国第一个世界遗产。

比基尼环礁被德国航海家及探险家Otto von Kotzebue发现之时，本来被命名为Eschscholtz环礁，以纪念波罗的海德国裔科学家Johann Friedrich von Eschscholtz。

Bikini Atoll (pronounced /ˈbɪkᵻˌniː/ or /bᵻˈkiːni/; Marshallese: Pikinni, [pʲi͡ɯɡɯ͡inʲːii̯], meaning coconut place) is an atoll in the Marshall Islands. The atoll consists of 23 islands totaling 3.4 square miles (8.8 km) surrounding a deep 229.4-square-mile (594.1 km) 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). Within Bikini Atoll, Bikini, Eneu, Nam and Enidrik islands comprise just over 70% of the land area. Bikini and Eneu are the only islands of the atoll that hosted a permanent population. Bikini Island is the northeastern most and largest islet. Before World War II, the atoll was known by its Baltic German name as Eschscholtz Atoll.