This article surveys Australian citizenship: its distinctive characteristics in the first half of the twentieth century, and how these were changed by the experience of the two world wars. It argues that Australian citizenship, at the time of Federation, was racially exclusive, imperial, masculine and deeply anchored in the traditional view of the military obligation of the individual to the state. The world wars, especially the war of 1939-45, encouraged some adjustment to these ideas, particularly in terms of the imperial link, women's status and the social rights of Australians. However, these conflicts were fought within a context of imperial loyalty and the intensity of their demands reinforced military service in defence of the nation as the primary civic virtue. The centrality of Anzac to Australian nationalism also perpetuated a gendered dimension to Australian citizenship. The world wars therefore, for all their dramatic impact on the lives of Australian families and the national political culture, did not force a major reconceptualisation of Australian citizenship.