Kožljak (Kozljak, Italian: Cosliacco, German: Waxenstein) is a village in Istria County, Croatia, in the municipality of Kršan.

Vladimir Nazor inspired by castles story wrote ballad Krvava košulja and novel Krvavi dani.

The count Albert III gave it in the second half of 14th century to Filip of Gutenegg (fort Guteneck, Gvothnic, Gotnik) family.

As his heir had no son, the hereditary rights were transferred on his daughters so the castle in 1529 came into dual possession of Castellano Barbo and Jakov Nikolić.

The son of Jakov, Josip, known for arrogance and cruelty, was murdered in 1574 by the rebel villagers, and his line extinguished with Ivan in 1600, when the castle has entirely become the property of Barbo family, whose member Francesco Barbo stood out particularly as made the castle the center of Protestantism in Istria, and cherished the Glagolitic cultural tradition from before.

It consisted of defensive walls, and the main gate led to a small yard, from the south closed by bastion, while north by the fort, with two towers.

Outside the walls at the graveyard are two more chapels, of St. George, in which is plate with Glagolitic inscription from 1590, and of the Holy Cross, created with a Baroque upgrade of chancel to medieval nave.