Altensteig (German pronunciation: [ˈaltn̩ʃtaɪk]; Swabian: Aldaschdaeg) is a town in the district of Calw, in Baden-Württemberg, Germany.

[2] The city (Stadt) of Simmersfeld is located at the south-western edge of the district of Calw, in the German state of Baden-Württemberg.

Altensteig's municipal area is located mostly in the Black Forest, though a portion of its eastern mass lies in the Upper Gäu [de].

There are also 15 villages in the municipal area: Bahnhof Berneck, Baiermühle, Bruderhaus, Chausseehaus, Elektrizitätswerk, Fischhaus, Heselbronn, Internationales Forum Burg Hornberg, Kohlsägmühle, Lengenloch, Lohmühle, Monhardt, Trögelsbach, Ziegelhütte, Zumweiler.

This coat of arms first appeared on a town seal in 1604, and was modified in 1935 with the addition of the stag antler to reference Württemberg.