Celje is the third-largest city in Slovenia and serves as a regional center for the traditional Slovenian region of Styria. It functions as the administrative seat of the Urban Municipality of Celje.
The town is situated in the lower Savinja Valley at the confluence of the Savinja, Hudinja, Ložnica, and Voglajna rivers. It is located below Upper Celje Castle and sits at a strategic road crossing connecting Ljubljana, Maribor, Velenje, and the Central Sava Valley.