Challenging conventional historiographies which claim that empire served only to hamper Australia’s national development and which examine only the Anglo-Australian connection, this book draws together for the first time several underutilized archives and emerging literatures to produce a new imperial history of Australia. It is one that places Australian settler colonialism in a broader imperial context while differentiating Australia’s categories for understanding the imperial world from those of London. This book demonstrates that many Australians came to view Britain’s empire not simply as a Greater British world state presided over by London, but as a global, ultramarine republic in which Australian settlers were co-equals. With this vision in mind, Australian settlers developed their own distinct categories for evaluating, criticizing, and claiming empire, ones based on settler logics that often placed race above gender, class, or nationality. Drawing on Australia’s many settler periodicals and official records, The imperial Commonwealth argues that this vision shaped colonial Australians’ understandings of the means and ends of their own settler colonialism came to define their relationship to Britain and motivated them to forge new transimperial connections with other settler and subject colonies in the Pacific, Africa, and South Asia through technology, humanitarianism, and military endeavour. By formulating, challenging, refining, and ultimately translating their own ideal of empire into colonial culture, politics, and law, Australian settler colonists transformed the Commonwealth into an empire in its own right.