Kostajnica
Kostajnica can refer to:
- Kostajnica, Bosnia and Herzegovina, a town on the right bank of river Una, in Bosnia
- Hrvatska Kostajnica, a town on the left bank of river Una, in Croatia
- Kostajnica (Doboj), a village near Doboj, Bosnia and Herzegovina
- Kostajnica (Konjic), a village near Konjic, Bosnia and Herzegovina