Barbara Zápolya was Queen of Poland and Grand Duchess of Lithuania as the first wife of King Sigismund I the Old from 1512 to 1515. Marriage to Barbara represented an alliance between Sigismund and the House of Zápolya against the Habsburgs in succession disputes over the throne to the Kingdom of Hungary. The alliance was short-lived as the renewed Muscovite–Lithuanian War forced Sigismund to look for Habsburg allies. The marriage was loving, but short. Barbara was the mother of Hedwig, Electress of Bradenburg, but died soon after the birth of her second daughter Anna.

Sigismund I the Old was King of Poland and Grand Duke of Lithuania from 1506 until his death in 1548. Sigismund I was a member of the Jagiellonian dynasty, the son of Casimir IV and younger brother of Kings John I Albert and Alexander I Jagiellon. He was nicknamed "the Old" in later historiography to distinguish him from his son and successor, Sigismund II Augustus. Before ascending to the Polish and Lithuanian thrones, he was Duke of Głogów from 1499, Duke of Opava from 1501, and governor of Silesia from 1504 on behalf of his brother, King Vladislaus II of Bohemia and Hungary.