Altendorf can mean any of the following:
- Altendorf, Schwyz, a municipality in Switzerland
- Altendorf, Upper Franconia, a town in the district of Bamberg, Bavaria, Germany
- Altendorf, Upper Palatinate, a town in the district of Schwandorf, Bavaria, Germany
- Altendorf (Kirnitzschtal), a village in Kirnitzschtal municipality, Saxony, Germany
- Altendorf, Austria, a town in the district of Neunkirchen in Lower Austria
- Altendorf GmbH, a woodworking machinery manufacturer from Minden, North Rhine-Westphalia, Germany
- Altendorf (megalithic tomb), an archaeological site near Naumburg, Hesse, Germany