Styria (Slovene: Štajerska; German: Untersteiermark), also Slovenian Styria or Lower Styria, is a traditional region in northeastern Slovenia, comprising the southern third of the former Duchy of Styria. The population of Styria in its historical boundaries amounts to around 705,000 inhabitants, or 34.5% of the population of Slovenia. The largest city is Maribor.

The Duchy of Styria, which existed as a distinct political-administrative entity from the 12th century to 1918, used to be divided into three traditional regions: the northern two-thirds of the former duchy, known historically as Upper and Central Styria, have been German-speaking and today form the Austrian State of Styria (German: Steiermark). The southernmost third of the former duchy, known as Lower Styria, was predominantly Slovene speaking and is today part of Slovenia.

According to the last Austrian census of 1910, Lower Styria had around 477,000 inhabitants, of which 85% were Slovene and 14% German speakers. In 1918, after the disintegration of the Austrian-Hungarian Empire following World War I, the Duchy of Styria was divided between the newly established states of German Austria and the State of Slovenes, Croats and Serbs. Rudolf Maister, a Slovene major of the former Austro-Hungarian Army, occupied the town of Maribor in November 1918 and claimed it to the State of Slovenes, Croats and Serbs. After a short fight with German Austrian provisional units, the current border was established.

Styria (/ˈstaɪəriə/; German: Steiermark, German pronunciation: [ˈʃtaɪ.ɐmaʁk] ( listen), Slovene: Štajerska, Hungarian: Stájerország) is a state or Bundesland, located in the southeast of Austria. In area it is the second largest of the nine Austrian federated states, covering 16,401 km². It borders Slovenia as well as the other Austrian states of Upper Austria, Lower Austria, Salzburg, Burgenland, and Carinthia. The population (as of 2011) was 1,210,700. The capital city is Graz (255,000 inhabitants).

The term "Upper Styria" (German: Obersteiermark) used by an Austrian refers to the northern and northwestern parts of the federal-state (districts Liezen, Murau, Judenburg, Knittelfeld, Leoben, Bruck an der Mur, and Mürzzuschlag). The term "West Styria" (Weststeiermark) is used for the districts to the west of Graz (Voitsberg, Deutschlandsberg, western part of the district Leibnitz), the districts east of Graz (Weiz, Hartberg, Feldbach, Fürstenfeld, and Radkersburg) are referred to as "East Styria" (Oststeiermark). The western and eastern parts of the district Graz-Umgebung may or may not be considered parts of West and East Styria, respectively. The southern parts of the Duchy of Styria, which have formed part of Slovenia since 1918, were (and sometimes colloquially still are) referred to as "Lower Styria" (Untersteiermark; Slovene: Štajerska).

Slovenia (ⁱ/sloʊˈviːniə/ sloh-VEE-nee-ə, Slovene: Slovenija), officially the Republic of Slovenia (Republika Slovenija,  [reˈpublika sloˈveːnija]) is a Slavic nation state, situated in South-Central Europe, at the crossroad of main European cultural and trade routes. It borders Italy to the west, Austria to the north, Croatia to the south and southeast, and Hungary to the northeast. It covers 20,273 square kilometres (7,827 sq mi) and has a population of 2.05 million. It is a parliamentary republic, member of the European Union and NATO. Relative to its geography, history, economy, culture, and language, it is a very diverse country distinguished by a transitional character. It is characterised by a high economic and social level. Its capital and largest city is Ljubljana.

The territory of Slovenia is mainly hilly or mountainous and has an exceptionally high landscape and biological diversity and a mosaic structure, which are a result of natural attributes and the long-lasting presence of humans. Four major European geographic units interweave here: the Alps, the Dinaric Alps, the Mediterranean, with a small portion of coastline along the Adriatic Sea, and the Pannonian Plain. The climate is temperate and significantly influenced by the variety of territory, with a strong interaction of the continental climate, the sub-Mediterranean climate and Alpine climate across most of the country. The country is one of the water-richest in Europe, with a dense river network, a rich aquifer system, and significant karstic underground watercourses. Over half of the territory is covered by forest.