Kostanjevica na Krki is a small town situated in the historic Lower Carniola region of southern Slovenia. It serves as the administrative seat of the Municipality of Kostanjevica na Krki and is currently part of the Lower Sava Statistical Region.
The settlement is located in the northern foothills of the Gorjanci Hills, positioned near the border with Croatia. The town center is uniquely situated on an island within the Krka River. Due to its geography and layout, it is promoted as the "Venice of Lower Carniola" in Slovenia.