This chapter discusses the import of philosophical discussions of ontology for organisational studies. It analyses the ontological presuppositions of positivism that still permeate much of sociology and organisational studies. These ontological presuppositions are then discussed from philosophical perspectives that propose or presuppose different ontologies: interpretivism; Heideggerian ontology; negative ontology and realism. The chapter then traces how these philosophical debates are reflected and extended in the field of organisational studies. The following approaches are discussed: positivism, Marxism, critical realism, post-foundational approaches, actor (...) network theory, process perspectives, postcolonial critique, ethnomethodology and symbolic interactionism. We conclude by highlighting promising developments at the intersection of ontology and organisation studies: encouraging multiple methods of enquiry; asking ‘what is’, ‘how did’ and ‘what does it do’ questions; reflecting on ontology’s ethical and political implications; and refining the sensitivity and coherence of future studies of organisations. (shrink)