Abstract: Judicial supremacy is a concept frequently employed in both domestic and comparative constitutional theory but rarely carefully defined and systematically analyzed. Moreover, it is not always used in uniform fashion but rather in somewhat different ways in different contexts. This chapter attempts to provide a systematic analysis of the concept and to evaluate its usefulness in the toolbox of comparative constitutional theory. Part I identifies and disaggregates four distinct senses of judicial supremacy. Part II illustrates the multiple meanings by looking at recent resolutions of the same-sex marriage issue by different institutions and mechanisms in many constitutional systems over the past decade. Part III assesses the utility of judicial supremacy as a concept by asking what and how much is at stake in the debates between each conception and its critics. It concludes that, as properly delimited, it is indeed a useful, non-unitary concept but its essential status in the field likely turns on further comparative experience.