Sevnica is a town on the left bank of the Sava River in central Slovenia. It is the seat of the Municipality of Sevnica. It is one of the three major settlements in the Lower Sava Valley. The old town of Sevnica lies beneath Sevnica Castle, which is perched on top of Castle Hill, while the new part of town stretches along the plain among the hills up the Sava Valley, forming another town core at the confluence of the Sevnična and Sava rivers.