Türnitz is a town in the district of Lilienfeld, in the Austrian state of Lower Austria. It lies in the Alpine foothills region of the state, within the Mostviertel quarter of Lower Austria.
The town is situated in the Traisen valley, along the river of the same name, and is surrounded by the wooded hills of the Türnitzer Alpen (Türnitz Alps), a range that forms part of the broader Eastern Alps. This setting has long given the area a role in forestry and, more recently, in outdoor recreation such as hiking and mountain biking.
Like many communities in the Lilienfeld district, Türnitz is a small, rural municipality with a population in the low thousands. It is connected to the regional road and rail network that links the Traisen valley to the provincial capital of Sankt Pölten to the north.