The present study offers an epistemological and ontological historiographical review of the concept of the unit of analysis using island archaeology as a case study. We carry out a critical investigation to lay out the main ideas used to define units of analysis, and we consider the discourse that has emerged between this and other fields when defining such a concept. From an epistemological point of view, we can define three distinct strategies: first, those that define units of analysis by their outer limits, their borders; secondly, those that make the definition based on the internal dynamics taking place within the units of study; and in third place, strategies that focus on defining the analytical unit as a set of interactions between agents. From a more ontological point of view, we can differentiate between strategies that take on a categorical perspective and those that take on a more relational perspective. Ultimately, we reflect on the conceptualization and function of the unit of analysis in the process of interpretation, and in so doing, we provide evidence of the great theoretical richness of the concept and the multiple interrelated factors involved in its development.