Istanbul is in Turkey.
Istanbul ( [ ˌɪstænˈbʊl ] , [ - ˈbuːl ] or [ - stɑːn - ] İstanbul [ isˈtɑnbuɫ ] ) , historically known as Constantinople and Byzantium , is the most populous city in Turkey and the country 's economic , cultural , and historic center . Turkey ( Türkiye Cumhuriyeti [ ˈtyɾcije d͡ʒumˈhuɾijeti ] ) , is a transcontinental country in Eurasia , mainly in Anatolia in Western Asia , with a smaller portion on the Balkan peninsula in Southeast Europe .