The Principality of Transylvania (; ; ) was a semi-independent state, ruled primarily by Hungarian princes. Its territory, in addition to the traditional Transylvanian lands, also included eastern regions of Hungary, the so-called Partium. The establishment of the principality was connected with Treaty of Speyer. However Stephen Báthory's status as king of Poland also helped to phase in the name Principality of Transylvania. It was usually under the suzerainty of the Ottoman Empire; however, the principality often had dual vassalage (Ottoman Turkish sultans and the Habsburg Hungarian kings) in the 16th and 17th centuries.