Australia, like most Western countries, has undergone profound demographic changes since 1901. The most significant transformations have been the sizeable growth in population, declining fertility and mortality, substantial immigration, population ageing, and the spatial redistribution of people between the States and Territories. This article examines how the Australian Constitution has dealt with the deep processes of demographic change that have reshaped the Australian population over the course of a century. Demography was in its infancy as a scientific discipline when the Constitution was drafted in the 1890s, yet the founders showed an understanding of rudimentary aspects of population dynamics. They anticipated population growth, interstate migration, the role of international immigration in shaping the Australian community and the importance of population statistics. However, in other respects, they introduced constitutional rigidities that have impeded the capacity of government to adapt to population change. This article charts the areas of demographic foresightedness and short-sightedness in the Constitution. It concludes by considering how a constitution might be designed to provide a sound framework for governance that is responsive to population dynamics.