亚特兰蒂姆帝国（英文：Empire of Atlantium）位于澳洲新南威尔士悉尼金克劳斯区的那威一座楼房，是一个提倡无疆界政府的组织。它亦被称为「全球最微型国家」，「国土」面积只有61平方米，于1981年11月27日「建国」。

亚特兰蒂姆帝国这些公民拥有相同价值观：推崇自由、享堕胎权利及安乐死。

「亚特兰蒂姆帝国国王」乔治·克鲁克山克自称“乔治二世”，少年时决定创建「国家」，现时号称有200多名「公民」，他亦宣称其「帝国」是「合法、职能齐全、非领土性的微型国家」。其中一人成为其公民不到一星期，已被委任为“首席司法官”。

The Empire of Atlantium is a micronation and secular, pluralist progressive lobby group based in New South Wales, Australia.

Micronations: The Lonely Planet Guide to Home-Made Nations describes Atlantium as "a refreshing antidote to the reactionary self-aggrandisement of so many micronations", and "an extremely sophisticated nation-state experiment, as well as an entirely serious claimant to legitimate statehood". The book's entry on Atlantium notes its espousal of "progressive, liberal policies" and characterizes it as a "secular humanist utopia".