AESIS(Αἶδις, Strab.; Αἰδῖνος, App.), a river on the east coast of Italy, which rises in the Apennines near Matilica, and flows into the Adriatic, between Ancona and Sena Gallica; it is still called the Esino. It constituted in early times the boundary between the territory of the Senonian Gauls and Picenum; and was, therefore, regarded as the northern limit of Italy on the side of the Adriatic. But after the destruction of the Senones, when the confines of Italy were extended to the Rubicon, the Aesis became the boundary between the two provinces of Umbria and Picenum. (Strab. v. pp. 217, 227, 241; Plin. Nat. 3.14. 19; Mela, 2.4; Ptol. 3.1.22, where the name is corruptly written Ἄδιος; Liv. 5.35.) According to Silius Italicus (Sil. Ital. 8.446) it derived its appellation from a Pelasgian chief of that name, who had ruled over this part of Italy. There can be no doubt that the Aesinus of Appian (App. BC 1.87), on the banks of which a great battle was fought between Metellus and Carinas, the lieutenant of Carbo, in-B.C. 82, is the same with the Aesis of other writers.
In the Itinerary we find a station (AD AESIM) at the mouth of the river, which was distant 12 M. P. from Sena Gallica, and 8 from Ancona. (Itin. Ant. p. 316.)
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