The United Principalities of Moldavia and Wallachia, commonly called United Principalities or as Wallachia and Moldavia, was the personal union of the Principality of Moldavia and the Principality of Wallachia, formed on 5 February [O.S. 24 January] 1859 when Alexandru Ioan Cuza was elected as the Domnitor of both principalities, which were autonomous but still vassals of the Ottoman Empire and which resulted in the unification of both principalities. Wikipedia