Harghita County in the context of "Târnava Mare"

The Hungarian minority of Romania (Hungarian: romániai magyarok, pronounced [ˈromaːnijɒji ˈmɒɟɒrok]; Romanian: maghiarii din România) is the largest ethnic minority in Romania. As per the 2021 Romanian census, 1,002,151 people (6% of respondents) declared themselves Hungarian, while 1,038,806 people (6.3% of respondents) stated that Hungarian was their mother tongue.

Most ethnic Hungarians of Romania live in areas that were parts of Hungary before the Treaty of Trianon of 1920. Encompassed in a region known as Transylvania, the most prominent of these areas is known generally as Székely Land (Romanian: Ținutul Secuiesc; Hungarian: Székelyföld), where Hungarians comprise the majority of the population. Transylvania, in the larger sense, also includes the historic regions of Banat, Crișana and Maramureș. There are forty-one counties of Romania; Hungarians form a large majority of the population in the counties of Harghita (85.21%) and Covasna (73.74%), and a large percentage in Mureș (38.09%), Satu Mare (34.65%), Bihor (25.27%), Sălaj (23.35%), and Cluj (15.93%) counties.

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.

About 9.3% of Romania's population is represented by minorities (the rest of 77.7% being Romanians), and 13% unknown or undisclosed according to 2021 census. The principal minorities in Romania are Romani people, and Hungarians (Szeklers, Csangos, and Magyars; especially in Harghita, Covasna, and Mureș counties), with a declining German population (in Timiș, Sibiu, Brașov, or Suceava) and smaller numbers of Poles in Bukovina (Austria-Hungary attracted Polish miners, who settled there from the Kraków region in contemporary Poland during the 19th century), Serbs, Croats, Slovaks and Banat Bulgarians (in Banat), Ukrainians (in Maramureș and Bukovina), Greeks (Brăila, Constanța), Jews (Wallachia, Bucharest), Turks and Tatars (in Constanța), Armenians, Russians (Lipovans, in Tulcea), Afro-Romanians, and others.

To this day, minority populations are greatest in Transylvania and the Banat, historical regions situated in the north and west of the country which were former territorial possessions of either the Kingdom of Hungary, the Habsburgs, or the Austrian Empire (since 1867 the dual monarchy of Austria-Hungary until World War I).

The Olt (Romanian and Hungarian; German: Alt; Latin: Aluta or Alutus, Turkish: Oltu, Ancient Greek: Ἄλυτος Alytos) is a river in Romania. It is 615 km (382 mi) long, and its basin area is 24,050 km (9,290 sq mi). It is the longest river flowing exclusively through Romania. Its average discharge at the mouth is 174 m/s (6,100 cu ft/s). It originates in the Hășmaș Mountains of the eastern Carpathian Mountains, near Bălan, close to the headwaters of the river Mureș. The Olt flows through the Romanian counties of Harghita, Covasna, Brașov, Sibiu, Vâlcea, and Olt. The river was known as Alutus or Aluta in Roman antiquity. Olt County and the historical province of Oltenia are named after the river.

Sfântu Gheorghe, Râmnicu Vâlcea and Slatina are the main cities on the river Olt. The Olt flows into the Danube river near Turnu Măgurele.

The Székelys (pronounced [ˈseːkɛj], Székely runes: 𐳥𐳋𐳓𐳉𐳗‎), also referred to as Szeklers, are a Hungarian subgroup living mostly in the Székely Land in Romania. Of the Székelys of Bukovina, some are still living in their native villages in Suceava County in Bukovina, but a significant number of their descendants is currently living in Tolna and Baranya counties in Hungary and certain districts of Vojvodina in Serbia.

In the Middle Ages, the Székelys played a role in the defense of the Kingdom of Hungary against the Ottomans in their posture as guards of the eastern border. With the Treaty of Trianon of 1920, Transylvania (including the Székely Land) became part of Romania, and the Székely population was a target of Romanianization efforts. In 1952, during the communist rule of Romania, the former counties with the highest concentration of Székely population – Mureș, Odorhei, Ciuc, and Trei Scaune – were legally designated as the Magyar Autonomous Region. It was superseded in 1960 by the Mureș-Magyar Autonomous Region, itself divided in 1968 into two non-autonomous counties, Harghita and Mureș. In post-Cold War Romania, where the Székelys form roughly half of the ethnic Hungarian population, members of the group have been among the most vocal of Hungarians seeking an autonomous Székely region in Transylvania. They were estimated to number about 860,000 in the 1970s and are officially recognized as a distinct minority group by the Romanian government.