Stjepan Konzul Istranin (1521 — after 1568) was a 16th century Protestant reformator who authored and translated religious books to Čakavian dialect. Istranin was the most important Croatian language Protestant writer. Istranin was born in Buzet in 1521. At that time Buzet belonged to the Habsburg Monarchy and was under the jurisdiction of the Roman Catholic Diocese of Koper, which used the Old Slavonic language for liturgical texts.