Danubian Principalities (Romanian: Principatele Dunărene, Serbian: Dunavske kneževine) 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 Küçük 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 (1859). Alongside Transylvania, the United Principalities of Moldavia and Wallachia became the basis for the Kingdom of Romania, and by extension the modern Romanian nation-state.
In a wider context, the concept may also apply to the Principality of Serbia in terms of The Principalities of the Danube which came under the suzerainty (alongside Wallachia and Moldova) of the Porte from 1817.