As implementation scientists know well, evaluating fidelity is essential for researchers and practitioners when making sure they implement a plan as intended. However, the concept of fidelity remains unclear, given that various conceptualizations exist within and across disciplines. To help researchers and practitioners understand fidelity, a conceptual framework integrating definitions within and across disciplines is needed. The study we report on here aimed to review the many different terms for and definitions of fidelity to create such an integrated interdisciplinary conceptual framework. We performed a rigorous and structured literature review, known as a scoping review. The 77 documents included in this scoping review: (1) defined fidelity by the degree to which a plan is implemented as planned, and (2) discussed fidelity as a concept, definition, conceptualization, facet, dimension, conceptual framework, model, or theoretical model. We used techniques that will be familiar to interdisciplinarians to find the commonalities amid the differences, allowing us to propose an integrated framework for this sort of endeavor. The conceptual framework we propose includes consideration of levels, dimensions, and relationships between key terms in the reviewed literature. It also clarifies the concept of fidelity and provides details regarding reliable measures to evaluate it. This framework can be used by those in all disciplines seeking to assess fidelity. And we think it will be especially helpful to those working in interdisciplinary teams.