Kozjak is a common South Slavic toponym derived from koza ("goat") that may refer to:
Austria Kozjak, the Slovene name for or Geißberg, a mountain in the Karawanks in southern Austria
Bosnia and Herzegovina , a village near Lopare, Bosnia and Herzegovina
Bulgaria Kozjak or Kozyak, a medieval name of Obzor Kozyak, Bulgaria, a village in Silistra Province
Croatia Kozjak Island, an uninhabited islet near Lošinj, Croatia Mali Kozjak, a mountain on the Croatian Adriatic coast Veliki Kozjak, a mountain in the Croatian Dalmatian Zagora Kozjak, Bilje, a settlement in Croatian Baranja Kozjak Lake, the largest of the Plitvice Lakes Kozjak, Maksimir, a neighbourhood in Zagreb
North Macedonia , a mountain in North Macedonia Kozjak Hydro Power Plant, with an eponymous artificial lake in North Macedonia Kozjak, Resen, a village in Resen Municipality, North Macedonia Kozjak, Karbinci, a village in the Municipality of Karbinci, North Macedonia Kozjak (mountain near Pčinja), a mountain in North Macedonia and Serbia (Kozjačija), a region in North Macedonia and Serbia
Serbia Kozjak (mountain near Pčinja), a mountain in Serbia and North Macedonia (Kozjačija), a region in Serbia and North Macedonia Kozjak (Loznica), a village near Loznica, Serbia Novi Kozjak, a village near Alibunar, Serbia
Slovenia Kozjak Castle, a castle ruin near Trebnje, Slovenia Kozjak Mountains, north of the Drava Valley in northeastern Slovenia and southeastern Austria Kozjak subdialect Kozjak Pass, a mountain pass in the Kamnik–Savinja Alps in northern Slovenia
Settlements Kozjak, Mislinja, a village near Mislinja, Slovenia Kozjak nad Pesnico, a village in the Municipality of Kungota, northeastern Slovenia Kozjak pri Ceršaku, a village in the Municipality of Šentilj, northeastern Slovenia Paški Kozjak, a village in the Municipality of Velenje, northeastern Slovenia Kozjak, a hamlet of Zabukovje in the Municipality of Šentrupert, southeastern Slovenia