["R&D Management, EarlyView. ", "\nABSTRACT\nRadical innovation (RI) offers significant benefits, but the challenges encountered during its implementation can be formidable. Recent literature suggests the use of practices such as prototyping, experimentation, piloting, and demonstration to address these challenges through small‐scale, iterative approaches. While these practices are popular, they have not been specifically developed to counter the uncertainties inherent in RI. In addition, the fragmented nature of existing research has led to ambiguous conceptual boundaries between them. Furthermore, we lack a solid understanding of the role that the different practices should play in the different stages of the RI innovation development process. To address these gaps, we introduce the concept of radical innovation validation (RIV) and, based on comparative case study research, develop a comprehensive, process‐oriented and empirically grounded framework for RIV which is composed of three activity categories (i.e., concept validation, technical trials, and market demonstrations) and five core principles (i.e., materializing solutions to stimulate creative thinking, enhancing the dialog with stakeholders, continuous learning, fast and non‐confrontational hypotheses testing, scaling up in semi‐controlled environments). We show that each of the three RIV activity categories provides a distinct contribution to a specific stage of the RI development process, while the RIV core principles support value creation throughout the entire process.\n"]