Which is the largest lake in the world by surface area?

The largest lake in the world by surface area is the Caspian Sea. Despite its name, geography conventionally classifies it as a lake: a huge, landlocked and saline body of water covering about 371,000 square kilometres.

The Caspian lies between Europe and Asia, with coastlines belonging to Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. It is an endorheic basin, meaning it has no natural river outlet to an ocean. Most of its inflow comes from the Volga River, while water leaves mainly through evaporation.

Its water is brackish rather than fully marine, with salinity around 1.2 percent—roughly a third of average ocean salinity. The basin is a remnant of the ancient Paratethys Sea and contains distinct northern, middle and southern regions with major differences in depth, temperature and ecology.

The name causes the most common confusion. If the Caspian is excluded as a “sea,” Lake Superior is often given as the largest conventional lake, while Michigan–Huron can rank first when treated as one hydrological lake. Under the standard quiz definition, however, the Caspian is the accepted answer.