This chapter explores whether mature federations can change internally to such an extent that they no longer resemble vibrant federal polities but ‘degenerate’ into fairly standard national unitary states. The chapter focuses on Australia, and draws commentary from other jurisdictions. Australia’s federal system was established through the coming together of six-self-governing colonies in the Constitution of 1901. The Federation has been transformed by two factors. First, Australia has numerous executive integration and intergovernmental mechanisms, which often lead to the federal government being the key decision-maker on state issues. Second, financial arrangements are increasingly centralised. The chapter argues that the political culture and attitude of Australians has become more centralist, favouring national policies over state policies. There is increased harmonisation of government regulation and standardisation of public services, inter alia. The chapter finds that Australia’s states and territories have become regional arms of national policy-making and Australia has thus ‘degenerated’ as a federation.