Celje is the fourth-largest city in Slovenia. It is a regional center of the traditional Slovenian region of Styria and the administrative seat of the City Municipality of Celje. The town of Celje is located below Upper Celje Castle at the confluence of the Savinja, Hudinja, Ložnica, and Voglajna rivers in the lower Savinja Valley, and at the crossing of the roads connecting Ljubljana, Maribor, Velenje, and the Central Sava Valley. It lies 238 m (781 ft) above mean sea level (MSL).

Slovenia officially the Republic of Slovenia, is a country in southern Central Europe. Slovenia is bordered by Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the south and southeast, and a short coastline within the Adriatic Sea to the southwest. Slovenia is mostly mountainous and forested, covers 20,271 square kilometres (7,827 sq mi), and has a population of approximately 2.1 million. Slovene, a South Slavic language, is the official language. Slovenia has a predominantly temperate continental climate, with the exception of the Slovene Littoral and the Julian Alps. A sub-mediterranean climate reaches to the northern extensions of the Dinaric Alps that traverse the country in a northwest–southeast direction. The Julian Alps in the northwest have an alpine climate. Toward the northeastern Pannonian Basin, a continental climate is more pronounced. Ljubljana, the capital and largest city of Slovenia, is geographically situated near the centre of the country.