Aar, a river in Switzerland, rising in the Ober and Unter Aar Gletscher, W. of the Grimsel Hospice, has a fine fall of 200 feet near Handeck, takes a N.W. course to Meiringen, flows through the Lakes of Brienz and Thun, and thence past Berne, then turning somewhat abruptly N.E. passes Aarberg, Soleure, Aarau, and Brugg, where it is joined by the Limmat and Reuss, and enters the Rhine at the village of Coblentz (Confluentia), near Waldshut. From it the Aargau Canton in the N.W. of Switzerland derives its name.