The river Ticino (/tɪˈtʃiːnoʊ/ titch-EE-noh, Italian: [tiˈtʃiːno]; Lombard: Tesin; French and German: Tessin; Latin: Ticīnus) is the most important perennial left-bank tributary of the Po.

[1] The river rises in the Val Bedretto in Switzerland at the frontier between the cantons of Valais and Ticino right below the Nufenen Pass, is fed by the glaciers of the Alps and later flows through Lake Maggiore, which traverses the border to Italy.

[4][5] The Ticino arises from the many torrents that drain the mountain flanks on the eastern side of Nufenen Pass in the upper Val Bedretto.

In the Leventina, the Ticino flows through three terrain steps separated by two narrow gorges (Gola di Monte Piottino and Biaschina) and finally reaches the canton's floor near Bodio at around 320 m (1050 ft).

Shortly after, at Biasca (286 m (938 ft)), the river is joined by its first major tributary, the Brenno which flows from Passo del Lucomagno through the Valle di Blenio.

Before the Ticino passes west of the canton's capital, Bellinzona, the river converges with its second larger left tributary, the Moesa, originating below the Passo del San Bernardino and flowing through the Valle Mesolcina.

Now the Ticino turns almost westwards and flows through the perfectly flat Piano di Magadino, an important cultivation and nature reserve area the river generated itself by its own sediments over ten thousands of years, before it enters the Lago Maggiore at the lowest point of Switzerland at 193 metres (633 ft).

In Sesto Calende the river, now called Fiume Ticino, exits Lake Maggiore and meanders southwards, passing the Milano-Malpensa Airport in the east.

A paved road constructed in 1964 goes over the Passo della Novena and after some ten hairpins down about 500 m (1,600 ft) in altitude on its western side and then through the Ägenental in northeasten direction ultimately leading to the Obergoms, the upper half of the valley of the uppermost part the Rhône course.