Brusnik is an uninhabited volcanic island in the Croatian part of the Adriatic Sea.
[3] Brusnik is 320 m long, 205 m wide, and has 30 meter high cliffs.
In 1951, the island was declared a geological monument of nature.
Brusnik, along with Vis, Sveti Andrija and the neighbouring islet of Kamnik, Biševo, Jabuka and the Palagruža archipelago, forms part of the Croatian Offshore Islands Important Bird Area (IBA).
This was designated as such by BirdLife International because it supports significant breeding populations of Scopoli's and Yelkouan shearwaters, as well as of Eleonora's falcons.