Ontologies are becoming increasingly important as a knowledge-based resource for man and machines. Ontology is a veritable tool in computing for representing and thus preserving, domain knowledge for both human and machine processing. This paper builds a foundational ontology for Nigerian languages. Each language is annotated with its location information showing geo-political zone, states, and places where the Language originates. The ontology of Nigerian languages was built using the Methontology approach and specifically created using the Protégé 5.5.0 OWL editor. The Ontology was built on and evaluated using queries and a set of competency questions. The Nija-Onto was found to strongly align with its purpose of representing domain knowledge and thus provides visualized and highly tractable information on Nigerian languages.