The aim of this chapter is to examine the ontological nature of AI based on Aristotle’s metaphysical categories. Before introducing the latter and applying them specifically to artifacts, including AI, the chapter studies the nature of the whole AI system, including algorithms, as well as the social structures surrounding its development to argue that AI is an ‘abstract artifact.’ As the very term ‘artificial’ indicates, AI is a technical artifact. What is the ontological character of artifacts and specifically of AI? This is not an easy topic to address. From Aristotle’s time to the present, artifacts have been distinguished from natural things, but a ‘continuum problem’ emerges when dealing with natural and artificial things, and a growing body of literature delves into this issue.