Count of Illésháza (formerly Baron) István Illésházy (March 1541 - Vienna, May 5, 1609) was a Protestant nobleman, chieftain, palatine of Hungary between 1608 and 1609.
His father's illeshazai Tamás Illésházy, the deputy lord of Pozsony county, his mother, the noble Zsófia Földes.
In 1572 he married second wife, the widow of István Derzsi Szerdahelyi, Anna, the daughter of Péter Erdődy, a Croatian ban.
From 1584 he first became a royal councilor and then a court master, in 1582 he was appointed chief lord of the county of Liptov and acquired the castle of Lika.
In 1603 he was accused of high treason writings against the king, and the royal personal represent János Joó (and Miklós Istvánffy) did everything he could to convict him of insult.