As applied to the context of intellectual property thinking today, ‘the common law’ refers to a variety of different ideas, each of which contributes to a particular normative vision for the institution. These myriad understandings of the term in turn draw from different structural, institutional, and jurisprudential ideas that the common law has come to be associated with over the last several centuries. Accordingly, this chapter attempts to unbundle these different usages of the term in the law and economics of intellectual property in order to show what they each bring to the discussion. In particular, it examines the three dominant versions of the idea in the literature, which understand the common law as: (i) a method of lawmaking and legal reasoning; (ii) judge-made law; and (iii) state law. After examining these different strands in the legal literature it then connects them to relevant ideas and theories in both general law and economics, as well as the law and economics of intellectual property.