The Ostrovica Castle is a large medieval structure situated above the small village of Ostrovica near Kulen Vakuf, Bihać municipality, Bosnia and Herzegovina. Having been built on a heavily wooded ridge of a steep hill overlooking left bank of the shallow Una river, the castle was located on a strategic site connecting the northern and southern parts of the long Una valley.

The Kurjaković family, also known as the Counts of Krbava, were a Croatian noble family that originated from the noble tribe of Gusić. It formed at the end of the 13th century, as descendants of Kurjak. They reached their peak as magnates between mid-14th and mid-15th century, having tight connections and high official positions at the Hungarian royal court, and dissolution in 1531 when the estates of magnate Ivan Karlović went to Nikola III Zrinski. Two members were Ban of Croatia, as well two were founding members of Order of the Dragon.