Teniz (; ) is a lake in Mendykara District, Kostanay Region, Kazakhstan.
The lake is part of the most important wetlands of Northern Kazakhstan and is a Important Bird Area under threat.
Teniz lies in the Turgay Depression, about to the south of the KazakhstanâÂÂRussia border. It is an elongated lake, stretching from north to south for . Its maximum width is . Lake Karakamys is located close by at the northern end, as a continuation. Tuzkol salt lake is located to the SSE. River Ubagan flows northwards to the east of the lake's eastern shore. The lake freezes in the winter and is fed by snow and groundwater.
The lake lies roughly northeast of Borovskoy, the district capital, west of Krasnaya Presnya village and east of Tenizovskoye; the villages of Kamyshny and Talapker are located by the lakeshore.
There is thick reed growth around the lake. Every year there are thousands of migratory birds stopping over at the Teniz and Karakamys lakes during the spring and autumn migrations. The main fish species in the waters are crucian carp, wild goldfish and lake minnow.