Wallachia and Moldavia are united under Alexandru Ioan Cuza as the United Principalities, an autonomous region within the Ottoman Empire, which ushered the birth of the modern Romanian state.
Danubian Principalities (Romanian: Principatele Dunrene, Serbian: , romanized: Dunavske kneevine) was a conventional name given to the Principalities of Moldavia and Wallachia, which emerged in the early 14th century. The term was coined in the Habsburg monarchy after the Treaty of Kk Kaynarca (1774) in order to designate an area on the lower Danube with a common geopolitical situation. The term was largely used then by foreign political circles and public opinion until the union of the two principalities in 1859. Alongside Transylvania, the United Principalities of Moldavia and Wallachia became the basis for the Kingdom of Romania, and by extension the modern nation-state of Romania.In a wider context, the concept may also apply to the Principality of Serbia as one of The Principalities of the Danube, which came under the suzerainty of the Porte from 1817.
Wallachia or Walachia (; Romanian: Țara Românească, lit. 'The Romanian Land' or 'The Romanian Country', pronounced [ˈt͡sara romɨˈne̯askə]; archaic: Țeara Rumânească, Romanian Cyrillic alphabet: Цѣра Рꙋмѫнѣскъ) is a historical and geographical region of Romania. It is situated north of the Lower Danube and south of the Southern Carpathians. Wallachia is traditionally divided into two sections, Muntenia (Greater Wallachia) and Oltenia (Lesser Wallachia). Wallachia as a whole is sometimes referred to as Muntenia through identification with the larger of the two traditional sections.
Wallachia was founded as a principality in the early 14th century by Basarab I after a rebellion against Charles I of Hungary, although the first mention of the territory of Wallachia west of the river Olt dates to a charter given to the voivode Seneslau in 1246 by Béla IV of Hungary. In 1417, Wallachia was forced to accept the suzerainty of the Ottoman Empire; this lasted until the 19th century, albeit with brief periods of Russian occupation between 1768 and 1854.
In 1859, Wallachia united with Moldavia to form the United Principalities, which adopted the name Romania in 1866 and officially became the Kingdom of Romania in 1881. Later, following the dissolution of the Austro-Hungarian Empire and the resolution of the elected representatives of Romanians in 1918, Bukovina, Transylvania as well as parts of Banat, Crișana, and Maramureș were allocated to the Kingdom of Romania, thereby forming the modern Romanian state.