Alster is a tributary of the Elbe river in Northern Germany.
Alster may also refer to:
Alster (Itz), a river of Bavaria and Thuringia, Germany, tributary of the Itz Alster, Sweden, a locality in Värmland County, Sweden Der Club an der Alster, a German sports club in Hamburg German auxiliary Alster (A50) (1988), an intelligence ship of the German Navy Mathilda Alster, a fictitious character in the Japanese manga Beyblade a Shandy with lemonade called Alster in northern Germany SS Alster, a number of steamships