Isabella Jagiellon was a Polish princess and the Queen consort of Hungary who lived from 1519 to 1559. Born in Kraków to King Sigismund I and Bona Sforza, she married John Zápolya in 1539. Following her husband's death, she became a central figure in the political struggles over the Hungarian throne. Acting as regent for her infant son, John Sigismund, she navigated complex conflicts involving the Ottoman Empire and the Habsburgs, eventually ruling the eastern regions of the kingdom until her death in Alba Iulia.