Lake Razelm or Lake Razim (Romanian: Limanul Razim, Limanul Razelm) is the name of a large freshwater lagoon on the shores of the Black Sea in Romania, south of the Danube Delta and part of its World Heritage Site.

The northern subgroup contains freshwater Razelm and Lake Golovița, which are connected by a channel 3.1 km (1.9 mi) wide, whereas the southern group is made up of salt lakes.

When the Razelm/Golovița system was closed off from the sea in the late 1970s, this resulted in several changes to the ecological conditions of the system, including a decrease in salinity to almost zero, an increase in refreshment time to over a year, and episodes of eutrophication.

[3] Popina Island at the north end of the lake is an important refuge for many bird species and invertebrates.

The recent ecological study suggests that the Razim-Sinoie lagoon system is close to the good ecological status according to the requirements of the Water Framework Directive.