In this essay we compare Bentham’s theory with the two movements commonly labelled «Legal Realism»; American Legal Realism and Scandinavian Legal Realism. We claim that Bentham shares with both Scandinavian and American Legal Realists a commitment to ontological, semantic and methodological naturalism. This means that for him, as for the Legal Realists, 1) there is one and only one «natural» spatio-temporal framework; 2) all meaningful legal concepts must be directly analyzable in empirical terms or must be understood as functions referring to empirical phenomena; 3) the methods of jurisprudence must be continuous with those of natural sciences. The differences between Bentham and the Legal Realists are mainly due to the former’s attempt to redefine legal concepts in order to make utilitarian legal reform, and most of all codification of law, possible.