The purpose of this study is to report an ontology of emails containing speech act of request. This ontology was developed in the study following a consideration of the issues found from previous studies concerning pragmatic features in emails. Recently, researchers in the field of pragmatics have shown an increased interest in pragmatic features in emails. Despite many diverse findings about how emails are composed and how speech acts are realized in emails, there remain some issues with regard to analysis. One of the issues is that previous studies analyzed email data from different foci and by using variously named categories. Because of this, previous results tend to be too fragmented to be interpreted systematically. This study, therefore, developed an ontology of emails containing speech act of request in order to systematize the analysis foci and categories.