John Zápolya, or John Szapolyai (Hungarian: Szapolyai János or Zápolya János, Croatian: Ivan Zapolja, Romanian: Ioan Zápolya, Slovak: Ján Zápoľský; 1490 or 1491 – 22 July 1540), was King of Hungary (as John I) from 1526 to 1540. His rule was disputed by Archduke Ferdinand I, who also claimed the title King of Hungary. He was Voivode of Transylvania before his coronation, from 1510 to 1526.
John was the oldest son of Count Stephen Zápolya and his second wife, Hedwig of Cieszyn. Stephen Zápolya was descended from a Croatian noble family from Slavonia. Their family name was derived from the Croatian phrase “za polje” (literally translated as “behind field”). Stephen became one of the wealthiest lords in the Kingdom of Hungary after inheriting the large domains of his brother, Emeric Zápolya, in 1487. Stephen Zápolya’s marriage with the Silesian duchess, Hedwig, who was related to Emperor Maximilian I, increased the prestige of the Zápolya family.
Stephen Zápolya had no sons when Matthias Corvinus, King of Hungary, died on 6 April 1490, according to a contemporaneous report, but a charter issued in September 1491 already mentioned John, showing that John was born between the two dates. Stephen Zápolya became Palatine of the Kingdom of Hungary from 1492 until his death in 1499.
Vladislaus’s brother, King Sigismund Jagiellon of Poland, came to Hungary to mediate between the royal family and the Zápolyas in late June. Emperor Maximilian had already in September declared war on Hungary, because he wanted to protect his claim (acknowledged in the 1491 Peace of Pressburg) to succeed Vladislaus. The teenager Stephen Zápolya was made one of the commanders of the Hungarian army. During the war, the envoys of King Vladislaus and Maximilian signed a secret treaty on 30 March 1506 about the marriage of Vladislaus’s daughter, Anne Jagiellon, and Maximilian’s grandson, Ferdinand.