The analysis of the correspondence between the Viennese authorities and their envoys residing in Istanbul between 1541 and 1551, in conjunction with the documents issued by the Ottoman Porte, reveals a twofold perspective on the identity of Transylvania, and mostly in regards to its political, juridical and territorial status. Each of the two parties created and employed their own, contrasting images, which were justified by diplomatic and military reasons. In the diplomatic contacts with the Ottomans, the Viennese authorities included Transylvania in the formula: Regni Hungariae pars, quam regina Isabella cum eius filio et frater Georgius possident. By using this formula, Vienna highlighted two important aspects; Transylvania was part of the crown of Hungary; Transylvania and other territories pertaining to the kingdom were held by Queen Isabella, her son and George Martinuzzi. The status of Transylvania was completely omitted in the Viennese diplomatic texts; not even a hint of its incipient state form was ever mentioned. This is explaining why the Viennese diplomats went to great lengths in order to obliterate Transylvania’s name from their treaty with the Ottoman Porte in 1547. The same logic guided the cautious Viennese diplomacy in its dealings with the government of Transylvania, denying any state identity to the principality. In the Austrian correspondence with the Ottomans, Isabella was referred to as “Queen Isabella,” “the widow of late King John,” because as female she could never claim the crown of St. Stephen. In their direct correspondence with Isabella, the Austrians did not hesitate to use the formulas “most serene lady, Queen Isabella,” “the holiest lady Isabella, widow Queen of Hungary.” The governor Georgius Martinuzzi was referred to as “frater Georgius.”His official titles, which were given by the sultan and recognized by the Transylvanian estates, namely as governor, treasurer, or king’s lieutenant were never mentioned in the Viennese letters. The future prince, John Sigismund, was even less mentioned in the Austrian diplomatic correspondence. Denying any royal title to him, a gesture which, on the contrary, could have implied the recognition of his legitimate claim to the crown of Hungary, and implicitly of Transylvania, the diplomatic formulas called him “Stephan, son of former king John,” and only once, in a document from 1551. Even in 1559, when the Diet proclaimed him “John II, by divine mercy king of Hungary,” John Sigismund was called always by the Viennese officials, until 1570, “the son of King John” or “duke.”The Porte adopted an opposite position determined by similar diplomatic reasons. As a means of countering any pretence of legitimacy to King Ferdinand I of Habsburg over the lands of the crown of St. Stephen and Transylvania, but also as a way of keeping the Transylvanian authorities under control, the Ottoman documents used the formula “land (vilâyet/eyâlet) of Transylvania”, and “prince” (hakîm) or “king” (kîral) in order to refer to John Sigismund’s title. The sultan, who regarded Transylvania as his right of conquest, gave it to John Sigismund out of goodwill and for the loyalty towards the Porte, and nothing could be changed in this respect without the sultan’s consent.