Târgu Mureș in the context of "2021 Romanian census"

Transylvania (Romanian: Transilvania [transilˈvani.a] or Ardeal; Hungarian: Erdély [ˈɛrdeːj]; German: Siebenbürgen [ˌziːbm̩ˈbʏrɡn̩] or Transsilvanien; Transylvanian Saxon: Siweberjen) is a historical and cultural region in Central Europe, encompassing central Romania. To the east and south its natural border are the Carpathian Mountains and to the west the Apuseni Mountains. Broader definitions of Transylvania also include the western and northwestern Romanian regions of Crișana and Maramureș, and occasionally Banat. Historical Transylvania also includes small parts of neighbouring Western Moldavia and even a small part of south-western neighbouring Bukovina to its north east (represented by Suceava County).

Transylvania is known for the scenery of its Carpathian landscape and its rich history, coupled with its multi-cultural character. It also contains Romania's second-largest city, Cluj-Napoca, and other very well preserved medieval iconic cities and towns such as Brașov, Sibiu, Târgu Mureș, Bistrița, Alba Iulia, Mediaș, and Sighișoara. It is also the home of some of Romania's UNESCO World Heritage Sites such as the Villages with fortified churches, the Historic Centre of Sighișoara, the Dacian Fortresses of the Orăștie Mountains and the Roșia Montană Mining Cultural Landscape.

The Mureș (Romanian: [ˈmureʃ]) or Maros (Hungarian: [ˈmɒroʃ]; German: Mieresch, Serbian: Мориш / Moriš) is a 789-kilometre-long (490 mi) river in Eastern Europe. Its drainage basin covers an area of 30,332 km (11,711 sq mi). It originates in the Hășmașu Mare Range in the Eastern Carpathian Mountains, Romania, rising close to the headwaters of the river Olt, and joins the Tisza at Szeged in southeastern Hungary. In Romania, its length is 761 km (473 mi) and its basin size is 27,890 km (10,770 sq mi).

The Mureș River flows through the Romanian counties Harghita, Mureș, Alba, Hunedoara, Arad and Timiș, and the Hungarian county Csongrád. The largest cities on the Mureș/Maros are Târgu Mureș, Alba Iulia, Deva and Arad in Romania as well as Makó and Szeged in Hungary.

The Székely Land or Szeklerland (Hungarian: Székelyföld, pronounced [ˈseːkɛjføld], Székely runes: 𐲥𐳋𐳓𐳉𐳗𐳌𐳞𐳖𐳇; Romanian: Ținutul Secuiesc and sometimes Secuimea; German: Szeklerland; Latin: Terra Siculorum) is a historic and ethnographic area in present-day Romania, inhabited mainly by Székelys, a subgroup of Hungarians. Its cultural centre is the city of Târgu Mureș (Marosvásárhely), the largest settlement in the region.

Székelys (or Szeklers) live in the valleys and hills of the Eastern Carpathian Mountains, corresponding mostly to the present-day Harghita, Covasna, and parts of Mureș counties in Romania.

Mureș County (Romanian pronunciation: [ˈmureʃ], Romanian: Județul Mureș, Hungarian: Maros megye) is a county (județ) of Romania, in the historical region of Transylvania, with the administrative centre in Târgu Mureș. The county was established in 1968, after the administrative reorganization that re-introduced the historical județ (county) system, still used today. This reform eliminated the previous Mureș-Magyar Autonomous Region, which had been created in 1952 within the People's Republic of Romania. Mureș County has a vibrant multicultural fabric that includes Hungarian-speaking Székelys and Transylvanian Saxons, with a rich heritage of fortified churches and towns.

The Transylvanian Diet (German: Siebenbürgischer Landtag; Hungarian: erdélyi országgyűlés; Romanian: Dieta Transilvaniei) was an important legislative, administrative and judicial body of the Principality (from 1765 Grand Principality) of Transylvania between 1570 and 1867. The general assemblies of the Transylvanian noblemen and the joint assemblies of the representatives of the "Three Nations of Transylvania"—the noblemen, Székelys and Saxons—gave rise to its development. After the disintegration of the medieval Kingdom of Hungary in 1541, delegates from the counties of the eastern and northeastern territories of Hungary proper (or Partium) also attained the Transylvanian Diet, transforming it into a legal successor of the medieval Diets of Hungary.

The diet sessions at Vásárhely (now Târgu Mureș) (20 January 1542) and at Torda (now Turda) (2 March 1542) laid the basis for the political and administrative organization of Transylvania. The diet decided on juridical, military and economic matters. It ceased to exist following the Austro-Hungarian Compromise of 1867, when Transylvania was returned to the control of the Diet of the newly empowered Hungary.