Ontologies are widely used to represent knowledgeexplicitly but it is impractical to expect all individuals andorganisations to agree on using one or a small subset of ontologies.The adoption of multiple ontologies causes ontology mismatcheswhich make their inherent vocabularies andrelationships become inconsistent, resulting in di±culty for onesystem to understand and reuse these ontologies. To achieveknowledge sharing and reuse, ontology mediation is required toreconcile mismatches between heterogeneous ontologies. In thispaper, we investigate the application of ontology in knowledgemanagement (KM). Many KM approaches have been developedwith the purpose of managing organisational knowledge. However,these approaches only focus on managing intra-organisationalknowledge, which is inadequate in current businessenvironment because users are often required to access interorganisationalknowledge to complete their tasks. Theseapproaches also fail to collaborate with each other as theirdesigns are based on their own business and KM requirement inmanaging organisational knowledge. We argue that ontologyand its mediation methods can be used to overcome limitation ofnon-collaborative problem in which individual organisation isunable to reuse inter-organisational knowledge. An ontologybasedinter-organisational KM network is therefore proposed toallow organisations accessing and retrieving inter-organisationalknowledge of common domain.