This introductory chapter argues for the relevance of focusing on interlegal reasoning as a distinct conceptual category, bringing together interlegality and legal argumentation theory. It presents a conceptual framework (Sect. 2), taking stock of particularly relevant aspects of the concepts of legal pluralism (Sect. 2.1) and interlegality (Sect. 2.2). Afterwards, the concepts of interlegal reasoning and interlegal balancing are introduced (Sect. 3). To do so, a working conceptualisation (Sect. 3.1) is presented, followed by a concise depiction of the relevant contexts (Sect. 3.2), norms and scope (Sect. 3.3), and types (Sect. 3.4) of interlegal reasoning. Finally, the structure of the collection and the contributions which compose it are briefly presented.