The Toce (Italian pronunciation: [ˈtoːtʃe, ˈtɔːtʃe]; Lombard: Toss; Walser: Riiss) is a river in Piedmont , Italy, which stretches the length of the Val d'Ossola from the Swiss border to Lake Maggiore into which it debouches near Fondotoce in the commune of Verbania. The river is 83.6 kilometres (51.9 mi) long and is formed in the upper Val Formazza by the confluence of a number of torrents in the plain of Riale.

The source of one of these, the Gries, is situated on the Italian southern side of the Gries Pass ; another forms beneath the Passo di San Giacomo, others flow from little Alpine lakes such as Lago Castel and Lago di Sabbione.

South of La Frua the water of the river plummets 143 metres (469 ft) over the Cascata del Toce into the Formazza Valley, through which it flows before transversing Valle Antigorio after another series of cascades. Near Crevola d'Ossola the river Diveria flows into the Toce. At this point, the valley gets wider and is known as Val d'Ossola.