Gregory III Šubić of Bribir (Croatian: Grgur III Šubić Bribirski) (died in 1342 or 1356) was a member of the Croatian Šubić noble family, who married the Venetian noble Catherina Dandolo.
Gregory III Šubić was the son of Juraj II Šubić and the grandson of Paul I Šubić of Bribir, who was the most powerful Croatian noble at the end of the 13th century and in the beginning of the 14th century. Gregory III had three brothers: Juraj II Šubić, Mladen II Šubić and Paul II Šubić.