Stjepan Vukčić Kosača (1404–1466) is a Bosnian nobleman.

He is a member of the House of Kosača, a Grand Duke (Voivode) of Herzegovina, Lord of Zahumlje and Primorje and also Herzog of Serbian Saint Sava.

It is Stjepan's ducal title "Herzog" that gives rise to the name Herzegovina when he asserts the independence of the territory in 1435 and 1448.

The title is today carried in the name of the country Bosnia and Herzegovina, and in the name of the Bay of Kotor city of Herceg Novi.