Lake Peipus lies on the border of Estonia and Russia.
The lake is one of Europe’s largest transboundary lakes and forms part of the international boundary between Estonia to the west and Russia to the east. It is not a single uniform basin: Lake Peipus is the northern section, Lake Pskov is the southern section, and the narrow Warm Lake connects them.
Together, these waters cover about 3,555 square kilometers, making the system the fifth-largest lake in Europe by area. It is relatively shallow, with an average depth of about 7.1 meters. The lake drains northward through the Narva River into the Gulf of Finland.
Lake Peipus also has a major medieval historical association. On April 5, 1242, frozen waters hosted the Battle on the Ice, in which forces of the Novgorod Republic defeated the Teutonic Order. Latvia belongs to the wider drainage basin, but it does not border the lake itself.