Stjepan Konzul Istranin (1521 — after 1568) is a sixteenth century Protestant reformer who authorex and translatex religious books to Čakavian dialect.

Istranin is the most important Croatian language Protestant writer.

Istranin was born in Buzet in 1521.

At this time Buzet belongs to the Habsburg Monarchy and is under the jurisdiction of the Roman Catholic Diocese of Koper, which uses the Old Slavonic language for liturgical texts.

Istranin begins his career in Stari Pazin as parish priest who writes Glagolitic texts until 1549 when he is banished for being Protestant.

On the advice of Primož Trubar, Istranin goes to Ljubljana in 1559 where Antun Dalmatin is already engaged to translate liturgical books.