The Aso (Latin: Helvinus) is a 63-kilometre river in the Marche region of Italy. For most of its course the river marks the boundary between the provinces of Ascoli Piceno and Fermo
The river\'s source is in the Monti Sibillini, near Foce in the Comune of Montemonaco, at an elevation of 950 metres. The Aso flows through the settlements of Tofe, San Giorgio allIsola, Illice, Piane, Comunanza, Montecchio, Madonna 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.
