(1) Background: This article adopts an interdisciplinary perspective to analyse, examine, and reflect upon prominent health literacy (HL) understandings in childhood and youth. (2) Method: The conceptual analysis combined Rodgers' and Jabareen's approaches to conceptual analysis in eight phases. (3) Results: First, we present exploratory entry points for developing a child-specific HL understanding based on the six dimensions of a 'health-literacy 6D model'. Second, we describe and reflect upon five meta-level dimensions covering the HL definitions and models for children and youth found in the conceptual analysis. Third, we integrate our findings into a target-group-centred HL definition for children and youth. (4) Discussion/Conclusion: This article raises awareness for the heterogeneity of the current conceptual HL debate. It offers a multidisciplinary approach for advancing the existing understanding of HL. Four recommendations for future actions are deduced from the following four principles, which are inherent to the proposed target-group-centred HL definition: (a) to characterize HL from an asset-based perspective, (b) to consider HL as socially embedded and distributed, (c) to recognize that HL develops both in phases and in flexible ways, and (d) to consider the multimodal nature of health-related information. Further research is necessary to test the feasibility and applicability of the proposed definition and conceptual understanding in both research and practice.