 Natural language ontology is the study of the ontology (ontological categories, structures, and notions) implicit in natural language. Natural language ontology is part of “descriptive metaphysics” to use Strawson’s term (1959), as opposed to what Fine (2017a) calls “foundational metaphysics”, metaphysics whose interest is in what there ultimately is. Natural language ontology is a sub-discipline of both philosophy and linguistics, more specifically, of metaphysics and natural language semantics. It was recognized as a separate field of study relatively recently, through the development of natural language semantics over the last decades. At the same time, natural language ontology can be considered a practice that philosophers have engaged in throughout the history of philosophy when drawing on language in support of a metaphysical argument or notion. The ontology of natural language is to be distinguished from the ontology a speaker accepts on the basis of philosophical or naïve reflection or reasoning using language, as well as from the ontology that is reflected in cognition in general. The ontology of a natural language is thus best characterized as the ontology competent speakers implicitly accept by way of using the language.