Aa is the name of a large number of small European rivers.
The word is derived from the Old German aha, cognate to the Latin aqua, water (cf. German -ach). In German also Au and Aue exists with the same meaning, similar to å in North Germanic languages. It is also an English noun, beloved of Scrabble players, meaning a stream.
The following are the more important streams of this name:
- two rivers in Latvia, Lielupe (in German Kurländische Aa) and Gauja (in German Livländische Aa), both falling into the Gulf of Riga, near Riga, which is situated between them
- a river in the north of France, falling into the sea below Gravelines, and navigable as far as Saint-Omer
- a river of Switzerland, in German Aabach, in the cantons of Lucerne and Aargau, which carries the waters of Lakes Baldegg and Hallwil into the Aar.
- in Germany there are the Westphalian Aa, rising in the Teutoburg Forest, and joining the Werre at Herford, the Münster Aa, a tributary of the Ems, and others.
- in the Netherlands, a river in Groningen province that flows through Groningen city.
- in the Netherlands, a river in Noord-Brabant.