In this thesis, an ontology for the mineral exploration domain is designed and developed applying the Protégé ontology editor. The MinExOnt ontology includes a formal and explicit representation of the terms describing real objects, activities, and processes in mineral exploration. The stages used for these activities have various vocabularies, which are semantically modeled in this ontology with Web Ontology Language (OWL). The aim of the thesis is to show how ontologies can be designed and developed to help manage and represent geological knowledge. In addition to providing a general workflow for building the ontology, this thesis presents a simple user guide for the used software, including Protégé, used for ontology development, and Knoodl-OntVis, used for OWL visualization.