The Isar is a river in Tyrol, Austria and Bavaria, Germany. Its source is in the Karwendel range of the Alps in Tyrol; it enters Germany near Mittenwald and flows through Bad Tölz, Munich, and Landshut before reaching the Danube near Deggendorf. At in length, it is the fourth largest river in Bavaria, after the Danube, Inn, and Main. It is Germany's second most important tributary of the Danube after the Inn.