Blatina kraj Prožure, Nature protection site in Dubrovnik-Neretva County, Croatia.

Blatina kraj Prožure is a 2.2-hectare protected site centred on a brackish lake in a karst depression on the island of Mljet. The lake's surface fluctuates between 2 and 2.7 hectares, making it the smallest such lake on the island. Stone pine forest surrounds the water, and charophyte algae grow in the lake.

The site was declared a Site of Community Importance in July 2013, within Croatia's Natura 2000 network under the EU Habitats Directive. It covers 2.24 hectares, entirely on land, around a brackish lake in a karst depression on Mljet. Croatia's accession to the EU in July 2013 coincided with this designation.

The name Blatina comes from the Croatian word for a muddy or marshy pool, which describes the small brackish lake in the karst hollow. The site is one of the smallest of its kind on Mljet and is known among researchers for its beds of stonewort (Chara spp.), the vegetation that defines its protected habitat.

Access to the area requires permission from local authorities and proper equipment for observing wetlands. Visitors should prepare for wet ground conditions and wear sturdy footwear.

The lake is the smallest of its kind on Mljet, fluctuating between 2 and 2.7 hectares of brackish water in a karst depression. Only one habitat type is registered for the site: strongly oligo-mesotrophic waters with benthic Chara vegetation.