Aargau (/ˈɑːrɡaʊ/ AR-gow, Swiss Standard German: [ˈaːrɡaʊ] ), more formally the Canton of Aargau (German: Kanton Aargau; Romansh: Chantun Argovia; French: Canton d'Argovie; Italian: Canton Argovia), is one of the 26 cantons forming the Swiss Confederation. It is composed of eleven districts and its capital is Aarau.
Aargau is one of the most northerly cantons of Switzerland, by the lower course of the Aare River, which is why it is called Aar-gau ("Aare province"). It is one of the most densely populated regions of Switzerland.