John I Ernuszt

John Ernuszt, Sr. (Hungarian: csáktornyai Ernuszt János; died after 3 March 1476) was Ban of Slavonia from 1473 to 1476. He was born into a Jewish family in Vienna. He moved to Buda, the capital of the Kingdom of Hungary, and converted to Roman Catholicism. He became a purveyor to the royal court, which enabled him to meet Matthias Corvinus, King of Hungary. His career in the administration of royal revenues began in 1461, with responsibility for the collection of the thirtieth (a custom duty) in Pozsony County. He purchased copper mines in Upper Hungary (now Slovakia) in 1466.

Ernuszt inspired Matthias's reform of the royal revenues (especially the centralization of their administration and the abolishment of tax exemptions) in 1467. In the same year, the king made him royal treasurer. Six years later, he was appointed ban of Slavonia and became one of the barons of the realm. His most estates were confiscated in the early 1470s, but he had secured the aristocratic status of his family.