Arnstein may refer to:
- Arnstein, a town in Bavaria, Germany
- Arnstein Castle in Arnstein, Bavaria
- Arnstein, Saxony-Anhalt, a town in Saxony-Anhalt, Germany
- Arnstein Castle in Arnstein, Saxony-Anhalt
- Arnstein Abbey in Rhineland-Palatinate, Germany
- Arnstein Castle, Rhineland-Palatinate, predecessor of Arnstein Abbey
- Arnstein Castle in Ottendorf, Landkreis Sächsische Schweiz-Osterzgebirge, Saxony
- Arnstein Castle (Austria), 12th-century castle ruins in Austria
- Palais Arnstein, Vienna
- Arnstein Airport, Ontario
- Arnstein (personal name), a surname and a given name
- Sherry Arnstein