John Sigismund Zápolya or
Szapolyai (; 7 July 1540–14 March 1571) was
King of Hungary (as
John II) from 1540 to 1551, and again between 1556 and 1570, and the first
Prince of Transylvania from 1570 to his death. He was the only son of
John I,
King of Hungary, and
Isabella of Poland. John I had only been able to preserve parts of the
Kingdom of Hungary against his opponent,
Ferdinand I, with the support of the
Ottoman Sultan Suleiman the Magnificent. Before John Sigismund's birth, John and Ferdinand concluded a peace treaty which acknowledged Ferdinand's right to reunite the whole kingdom after John's death. However, John bequeathed his realm to John Sigismund on his deathbed, only two weeks after John Sigismund's birth. His father's staunchest supporters elected the infant John Sigismund king, but he was never crowned with the
Holy Crown of Hungary.