From a design science perspective, information systems and their components are viewed as artifacts. However, not much has been written yet on the ontological status of artifacts or their structure. After March & Smith's (1995) initial classification of artifacts in terms of models, constructs, methods and instantiations, there have been only a few attempts to come up with a more systematic approach. This conceptual paper provides an ontological analysis of the notion of artifact grounded in the foundational ontology UFO. Its core is an ontological characterization of artifacts, and technical objects in general from a Design Science Research perspective, developed in conversation with other approaches. This general artifact ontology is applied in a systematic classification of IS artifacts. We include practical implications for Design Science Research.