Bijeljina (; ) is a city and municipality in northeastern Republika Srpska, which is one of two entities of Bosnia and Herzegovina. The city is the second largest in the Republika Srpska entity after Banja Luka and the sixth largest city in Bosnia and Herzegovina (after Sarajevo, Banja Luka, Tuzla, Zenica and Mostar), and is situated on the plains of Semberija. Bijeljina is the unofficial centre of the eastern part of Republika Srpska, with 114,663 inhabitants. Bijeljina is located at from the border with Serbia and from the border with Croatia.