Plavnik is an unpopulated island in the Adriatic Sea, belonging to Croatia located between the Central Straits and the Kvarner Bay.

[2] This channel is the shortest route from the Adriatic Sea through the islands to Rijeka.

A lighthouse, established in 1890, sits at the northwestern point of the islet, marking the east side of the narrowest opening of the Krusija Channel.

In the middle of the straits between these islands and Plavnik, the sea depth is about 9 metres (30 feet).

Plavnik is home to birds such as the wheateaters, pheasant, and white-headed vulture.