Back جون جاجيلون ARZ Ян з княжатаў літоўскіх Byelorussian Ян з княжатаў літоўскіх BE-X-OLD Ιωάννης Γιαγκιέλλον Greek Jonas iš Lietuvos kunigaikščių Lithuanian Jan z Książąt Litewskich Polish Ян (княжич литовский) Russian
John of the Lithuanian Dukes (Jan Ochstat de Thelnicz, Lithuanian: Jonas iš Lietuvos kunigaikščių, Polish: Jan z Książąt Litewskich; 8 January 1499 – 18 March 1538) was Bishop of Vilnius (1519–36) and of Bishop of Poznań (1536–38). He was the bishop when Protestantism was making the first inroads into the Grand Duchy of Lithuania and took the first steps in combating it. John was an illegitimate son of Sigismund I the Old, King of Poland and Grand Duke of Lithuania, and his mistress Katarzyna Telniczanka.