A well-designed OWL ontology for the MPEG-7 standard has long been desired, yet not achieved for over nearly two decades due to modeling difficulties and ontology engineering challenges. The MPEG-7 Ontology presented on this website is the only formally grounded MPEG-7 ontology, which has been implemented in OWL, and checked for consistency with industry-leading reasoners, namely HermiT and FacT++. In contrast to previous OWL mappings of the XSD files of the MPEG-7 vocabulary, it captures the semantics of the standard via high expressivity while maintaining decidability. This ontology is suitable for the representation of images, audio, video, and to a limited extent, 3D scenes, still and moving regions of interest, as well as spatial, temporal, and spatiotemporal reasoning over multimedia contents. It exposes the entire MPEG-7 vocabulary through a compact, permanent URI, and unlike its predecessors, it provides a physical URI for each term. This approach enables excellent documentation for practitioners.