Which lake on the Estonia-Russia border is Europe's fifth-largest lake?

Lake Peipus is the lake on the Estonia–Russia border that ranks as Europe’s fifth-largest lake.

The lake covers about 3,555 square kilometers and is actually a connected system of three parts: Lake Peipus in the north, Lake Pskov in the south, and the narrow Warm Lake between them. Its deepest point is only about 15 meters, making it broad and relatively shallow.

Lake Peipus drains through the Narva River into the Gulf of Finland. Around 30 rivers and streams flow into it, including the Velikaya and Emajõgi. Its international location also gives it a notable historical role: on 5 April 1242, the frozen lake was the setting for the Battle on the Ice between Novgorod forces and the Teutonic Order.

A common mix-up is Lake Pskov, which is not a separate answer to this question but the southern section of the wider Lake Peipus system. The lake’s European ranking is based on surface area and places it behind Lakes Ladoga, Onega, Vänern, and Saimaa.