Lake Atanasovsko or Lake Atanasovo (Bulgarian: Атанасовско езеро, Atanasovsko ezero) is a salt coastal lake north of Burgas, Bulgaria, located in direct proximity of the Black Sea. The lake is about 5 km long and divided into two by a strip of sand in the middle. The lake is particularly known for the diversity of flora and fauna and is surrounded by swamps and canals that drain the whole local basin into the sea.
Due to the water of Lake Atanasovsko's high salt content that increases every year because of the link with the sea, salt has been produced in it since 1906, with 40,000 tons of sea salt being obtained a year. The lake's north part, a nature reserve since 1980, is connected by a canal to the Black Sea, while the smaller south one that is mostly used for salt production is a buffer zone to the reserve. A road connecting Varna with Burgas passes through the sand strip in the middle of the lake.
The lake is home to over 230 species of vascular plants, of which 7 endangered in Bulgaria. It is also inhabited by the Etruscan pygmy shrew, the smallest mammal by mass. Lake Atanasovsko is also one of the key ornithological locations in the country, with 314 species of birds being present, 70% of all in Bulgaria. 12 of them are globally endangered, including the pygmy cormorant, the red-breasted goose, the ferruginous duck, the Dalmatian pelican and the corn crake. In addition, 17 local species of birds in danger of extinction in Bulgaria also live in the lake, such as the common tern and the Audouin's gull. The high number of birds is due to the lake's location on the important Via Pontica bird migration route, the lake being most populated by birds during the autumn migration.