Organisations are increasingly transforming themselves to remain profitable and obtain sustainable competitive advantages. Business processes are as important as technology in promoting organisational transformation. Organisational transformation ultimately entails combining existing business components, whether or not with the same use and design, with new ones to generate novel products and services. For example, one particular type of organisation transformation is digital transformation. This notion, which covers even the subjective aspects of organisational transformation, is currently under intensive discussion and suffers from the (...) semantics terms fluctuation related to the notion of ‘organisational transformation’. We argue that this topic could strongly benefit from an ontological analysis and conceptual clarification of these notions. This paper contributes with an attempt in this direction by proposing a Core Ontology of Organisational Transformation (COOT). This ontology comprises concepts and relations central to creating a reference model representing the organisational transformation paradigm. COOT was applied in a real-world case study on a car rental company. (shrink)