The Internet of Things (IoT) is rapidly expanding, connecting billions of devices and offering new possibilities in many different contexts. However, it is also exposed to significant cybersecurity risks due to the unique characteristics of such interconnected and complex systems. Existing threat modeling approaches are often designed for traditional ICT environments and they struggle to address the complexity of IoT systems. This thesis proposes an ontology-driven framework to automate threat modeling for IoT systems, enabling more effective and efficient security assessments. This framework is built upon an ontology, developed using OWL 2 (Web Ontology Language) and Protégé. The ontology provides a formal representation of IoT systems, modelling their components, interactions, and potential threats.