Karlstein may refer to places in:
; Germany:
- Karlstein am Main, a municipality in Landkreis Aschaffenburg, Bavaria
- part of Bad Reichenhall, Bavaria
- a rock with a ruin there
- Karlstein bei Hornberg, a rock in Hornberg, Baden-Württemberg
- part of Regenstauf, Landkreis Regensburg, Bavaria
- Schloss Karlstein, the castle there
- Aussichtspunkt Karlstein, a site above Weinstadt, Baden-Württemberg
; Austria:
- Karlstein an der Thaya, a municipality in Lower Austria, Austria
- Schloss Karlstein, the castle there
- Internierungslager Karlstein an der Thaya, a former internment camp there
; Czech Republic:
- Karlštejn Castle, a 14th-century castle in Central Bohemia
- Karlštejn (Beroun District), městys named after the castle
- Karlštejn, nature reserve nearby the castle
- Hunting castle Karlštejn nearby village Svratouch in Pardubice Region (Chrudim District)
- Karlštejn, administrative part of village Svratouch, named after the hunting castle
- Karlštejn, hill in Žďárské vrchy where the hunting castle is situated
cs:Karlštejn (rozcestník)