Leonius

Leonius may refer to:
 * Léonin (fl. 1150s — d. ? 1201), the first known significant composer of polyphonic organum;
 * the author of a versified Historia Sacra, found in a manuscript of the Bibliothèque Nationale in Paris (see Leonine verse)
 * the probably apocryphal inventor of Leonine verse, if different from either or both of the preceding two persons
 * Leonius (Dean of Wells), fl. 1213