Stephen Báthory
Multiple members of the Bathory family of Hungary were named Stephen.
The first Stephen Bathory (1477-1534) in 1529 became governor of Transylvania.
His youngest son Stephen Bathory (1533-1586) was king of Poland from 1575-86. He was succeeded as prince of Transylvania by his brother, Christopher Bathory (1530-81).
Stephen was elected to become king of Poland, after Henry III of Valois returned suddenly to France. He married Anna, daughter of Sigismund II Jagiello.
Stephen Bathory, upon becoming king of Poland, attacked and tried to take Danzig by military force. Danzig successfully defended against him and Bathory had to accept Danzig's continued status as independent city state. He verified this in 1577.
Stephen Bathory planned a Christian alliance against the Ottomans. He also tried to make Russia a vassal state of Poland. He considered this a necessary step for his anti-Ottoman crusade.
When Stephen Bathory died, there was a one year interregnum, which ended with the appointment of a Jew, Saul Wahl, as king of Poland. His reign lasted a single day and he was succeeded by Sigismund III Vasa of Sweden.
The other son of the first Stephen Bathory was also called Stephen Bathory. He was prince of Transylvania from 1571-75. He had succeeded John II Zapolya as prince of Transylvania.