Oxonium

Oxonium may refer to:
 * Oxonium ion, any ion which contains a tricoordinated oxygen atom, RR'R"O+
 * Oxonium, an IUPAC name for the simplest oxonium ion, hydronium, H3O+
 * Oxonium (often abbreviated to Oxon.), sometimes used in university circles as a Latin name for Oxford University in England