Background and Objective: With the social prescribing movement rapidly spreading across the globe, there is a need for an agreed definition of social prescribing. As there are two types of definitions – conceptual and operational, agreement on both types of definitions is needed. The aim of this study was to establish internationally accepted conceptual and operational definitions of social prescribing. Methods: A three-round Delphi study was conducted with an international, multidisciplinary panel of experts. The expert panel (n=48) represented 26 different countries across five continents, numerous expert groups, and a variety of years of experience with social prescribing. Consensus was defined a priori as ≥80% agreement. In Round 1, participants were asked to list key elements that are essential to the conceptual definition of social prescribing and to provide corresponding statements that operationalize each of the key elements. In Round 2, participants were asked to rate their agreement with items from the first round for inclusion in the conceptual and/or operational definitions of social prescribing. Based on the findings from this round, the conceptual and operational definitions of social prescribing were developed, including long and short versions of the conceptual definition. In Round 3, participants were asked to rate their agreement with the conceptual and operational definitions of social prescribing. Results: Internationally accepted conceptual and operational definitions of social prescribing were established. The Common Understanding of Social Prescribing (CUSP) conceptual framework was developed from the definitions. The CUSP acronym reflects the potential of this foundational work to bring about a point of transition in the social prescribing movement through the advancement of common understanding. Conclusions: This foundational work offers a common thread – a shared sense of what social prescribing is, which may be woven into social prescribing research, policy, and practice to foster common understanding of this concept.