Breitnau is a municipality in the district of Breisgau-Hochschwarzwald in Baden-Württemberg in southern Germany, about 30 kilometres from the city of Freiburg im Breisgau.

The municipality of Breitnau is very spread out, with many, scattered, farmsteads, some of the very large, most of which have farmhouses with half-hipped roofs, typical of the Black Forest.

The municipality of Breitnau incorporates the villages of Hinterdorf, Steig (since 1935 part of Breitnau) and Vorderdorf, the Zinken Beim Löwen, Bisten (partly also in Hinterzarten), Bruckbach, Eckbach, Einsiedel, Fahrenberg, Freyel, Hintereck, Hirschsprung, Höllsteig, Hohlengraben, Jungholz-Föhrwald, Löffeltal, Moos, Oberhöllsteig, Ödenbach, Posthalde, Ravenna(schlucht), Siedelbach (since 1860 part of Breitnau), Tiefen, Winterhalden and Wirbstein, the farms of Haberstrohhof, Holzhof, Kuhnenbach, Schuhmächerlehof and Zimmeracker and the houses of Bäuerleshütte, Birklehof, Eckerhäusle, Falkenfreyel, Hundsschachen, Jockelhäusle, Jörgenhäusle, Nessellachen and Paulyhäusle.

[3] Breitnau is first mentioned 1275 as Breittnowe but is probably older as the first church was built around 1200 and St. Oswald's Chapel was consecrated as early as 1148.

In 1688 the Margrave Louis William of Baden had schanzen built which were intended to block any invasion by the French.

[4] In 1755, the poor route through the Höllental was improved in order to enable the bridal procession of Princess Marie Antoinette to travel as much as possible on Anterior Austrian soil on her way to Paris.

Breitnau and its southern neighbour, Hinterzarten, form a joint administrative municipality (Vereinbarte Verwaltungsgemeinschaft) and tourist community.

The former railway stations of Hirschsprung, Posthalde and Höllsteig (near the Ravenna Gorge), which all lie within the municipality of Breitnau, are no longer served.

There is a path down the Ravenna Gorge, a steep, rocky side valley of the Hollental which leads to the Breitnau Plateau.