The Adige (Italian: Adige Italian pronunciation: [ˈa(ː)didʒe]; Venetian: Àdexe; Trentin: Ades; Friulian: Adis; German: Etsch; Ladin: Adesc, or Adiç; Latin: Athesis) is a river with its source in the Alpine region of Trentino-Alto Adige/Südtirol near the Italian border with Austria and Switzerland. At 410 kilometres (250 mi) in length, it is the second longest river in Italy, after the Po River with 652 kilometres (405 mi).

The river flows out of the artificial Alpine Reschensee, located at the Reschen Pass (1,504 metres (4,934 ft)) close to the borders with Austria and Switzerland above the Inn valley. The lake is known for the church tower that marks the site of the former village of Alt Graun ("Old Graun") that was abandoned and flooded in 1953 when the dam enclosing the headwaters was finished. Near Glurns, the Rom River from the Swiss Val Müstair joins.

The Adige then runs eastbound through the Vinschgau to Merano (this section is called Etschtal) where it is met by the Passer river from the north. South of Bolzano, the Eisack joins the river that is now heading south through a valley that always has been one of the major routes through the Alps, leading to and from the Reschen Pass and the Brenner Pass, at 1,370 metres (4,490 ft) considered the easiest of the main Alpine passes.

The Salurner Klause/Chiusa di Salorno narrows at Salurn marks the southern-most part of the German-speaking area. Thus, the Adige was mentioned in the Lied der Deutschen of 1841 as the southern border of the German language area of the time. This song was made the national anthem of Germany in 1922, after Italy took control of all of the Adige.

Near Trento, the Avisio, Noce, and Fersina rivers join. The Adige then crosses Trentino and later Veneto, flowing past the city of Verona and the towns of Rovereto and Adria through the Lagarina valley and the north-eastern part of the Po plain into the Adriatic sea. Both the Adige and the Po run parallel in the river delta without properly joining.

As a river in the mountains, it is subject to sudden swellings and overflows. It is also connected through artificial underground canals to Lake Garda for flood prevention.