Australia’s national system of social security reached its centenary in June 2008. This article provides a broad overview of how social security has developed in Australia over the last 100 years or so and reflects on how the system has come to be as it is now. Although much has changed in that time, there are strong elements of continuity as well—particularly the prevalence of means tests, the use of funding from general revenue, and the strong emphasis on participation. It is noted that Australian model of social security differs markedly from the international norm. Nevertheless, it has proven to be remarkably resilient since its inception a century ago such that arrangements akin to social insurance (the usual model elsewhere) have, as a result, mainly developed in the private sector. Maximising economic and social participation has also been a cornerstone of Australia’s system. The authors speculate that, given the relative stability demonstrated by the system so far, 100 years from now the essential elements of Australia’s social security system may well remain intact.