  Ladyman (1998) distinguished epistemic and ontic forms of structural realism, and many of those who have taken up structural realism have been philosophers of physics who have developed the latter. Others have made it clear that their structural realism is a purely epistemological refinement of scientific realism. On the other hand, Bas van Fraassen (1997, 2006, 2008) defends an empiricist and non-realist form of structuralism about science, motivated by an illuminating reconstruction of the origins of structuralism in the debate about the epistemology of physical geometry in the nineteenth century, and more generally in the progressive mathematisation of science. Yet more kinds of structuralism now abound in contemporary analytic philosophy. These include causal structuralism concerning the individuation of properties, mathematical structuralism concerning the nature of mathematical objects, and structuralism about laws and dispositions. The relationship between structural realism and these views is a matter for further work. While many realists and antirealists alike are agreed that the most viable form of scientific realism is structural realism, many others continue to defend other forms of scientific realism. This article reviews the issues and provides a guide for further reading.