This chapter is about Lacan’s discussions of Marx from the late 1960s and early 1970s. It reconstructs in detail the extended argument Lacan made about Marx during this period, and pays particular attention to the inter-connected positions Lacan gives to Marx, and to psychoanalysis, in the history of science. The chapter begins by summarising the idea put forward by Lacan in Seminar XVI: From an Other to the other (1968–69), that there is a ‘homology’ between his and Marx’s theories. It balances this, however, with the claim he makes shortly after, in Seminar XVII: The Other Side of Psychoanalysis (1969–70), that Marx ‘founded capitalism’. The chapter emphasises how Lacan gave Marx a fundamentally paradoxical status, which is closely related to the way Lacan also understood psychoanalysis at this point. The chapter ends with a close reading of Lacan’s 1970 radio interview ‘Radiophonie’, where he describes how both Marx and Freud brought about a particular kind of intervention within the historical logic of science. Lacan demonstrates here how psychoanalysis makes possible a new perspective on capitalism and science, by departing with Marx in significant ways.