The Aso (Latin: Asis) is a 63 km river in the Marche region of Italy. Its entire course falls within the Province of Ascoli Piceno. The river’s source is in the Monti Sibillini, near Foce in the Commune of Montemonaco, at an elevation of 950 metres. The Aso flows through the settlements of Tofe, San Giorgio all’Isola, Illice, Piane, Comunanza, Montecchio, Maonna del Lago, Aso and Rubbianello before entering the Adriatic Sea at Pedaso, where it delivers a mean discharge of 2.6 cubic metres per second.