The ambition of this article is threefold. First, it is to offer a realist reading of Aristotle's regime theory as it is laid out mostly in Books IV-VI of his Politics. The author argues that Aristotle's regime theory has three fundamentally realist claims about the workings of politics: first, the search for a perfect regime is not the only legitimate subject of political theory; second, every regime is built on a delicate balance of a particular understanding of political justice, a variety of sociological factors and the institutional design and political virtues of its politicians; third, there are almost as many different regimes as polities, and although they can be grouped into major regime types, there are many sub-types and mixed and transitory regimes. Second, the article argues that modern democratic theories have an unacceptable 'moralistic bias' from a realist point of view. Third, that a neo-Aristotelian regime theory can offer an attractive realist alternative to the predominant contemporary understandings of political regimes.