The Eisack (German: Eisack; Italian: Isarco; 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.