The Eisack (; ; Latin: Isarus or Isarcus) is a river in Northern Italy, the second largest river in South Tyrol. Its source is near the Brenner Pass, at an altitude of about 1990 m above sea level. The river draws water from an area of about 4,200 km². After about 96 km, it joins the Adige river south of Bolzano. At first the river flows though the Wipptal and after the village of Vahrn through the Eisacktal. Its source is sung of in the Bozner Bergsteigerlied as the northern frontier of the South Tyrolean homeland.

The Eisack (; ; Latin: Isarus or Isarcus) is a river in Northern Italy, the second largest river in South Tyrol. Its source is near the Brenner Pass, at an altitude of about 1990 m above sea level. The river draws water from an area of about 4,200 km². After about 96 km, it joins the Adige river south of Bolzano. At first the river flows though the Wipptal and after the village of Vahrn through the Eisacktal. Its source is sung of in the Bozner Bergsteigerlied as the northern frontier of the South Tyrolean homeland.