Lake Balkhash (Kazakh: Балқаш көлі, Balqaş kóli, Kazakh pronunciation: [bɑlqɑɕ kwʏlɪ]; Russian: озеро Балхаш, romanized: ozero Balkhash) is a lake in southeastern Kazakhstan, one of the largest lakes in Asia and the 15th largest in the world. It is located in the eastern part of Central Asia and sits in the Balkhash-Alakol Basin, an endorheic (closed) basin. The basin drains seven rivers, the primary of which is the Ili, bringing most of the riparian inflow; others, such as the Karatal, bring surface and subsurface flow. The Ili is fed by precipitation, largely vernal snowmelt, from the mountains of China's Xinjiang region.

The lake currently covers about 16,400 km² (6,300 sq mi). However, like the Aral Sea, it is shrinking due to diversion and extraction of water from its feeders. The lake has a narrow, quite central, strait. The lake's western part is fresh water. The lake's eastern half is saline. The east is on average 1.7 times deeper than the west. The largest shore city is named Balkhash and has about 66,000 inhabitants. Main local economic activities include mining, ore processing and fishing.

There is concern about the lake's shallowing due to desertification of microclimates and water extraction for multiplied industrial output.