Ala-Kul, Alpine lake in Issyk-Kul Region, Kyrgyzstan.

Ala-Kul is a rock-dammed lake on the northern slope of the Terskey Alatau range in Kyrgyzstan's Ak-Suu District, Issyk-Kul Region. It lies at 3,532 m in a narrow gorge on the right side of the Karakol Valley, measures 2.8 km long and 600–700 m wide, covers 1.5 km², and is more than 70 m deep. A glacier visible from the shore feeds it, and water seeps out under the natural dam into the Karakol River.

The lake was first documented in 1811 when Russian explorer Putimtsoff reached the area during an expedition to the region. About thirty years later, Alexander von Schrenk conducted a more thorough exploration and survey of the lake and surrounding mountain terrain.

The Kyrgyz name Ala-Köl means "variegated lake," but it probably comes from the Ala-Tau mountains to the north rather than from the water's colours. The Russian traveller Putimtsoff, who reached the lake in 1811, described rocks of different colours in the lake and furious winds blowing around it.

Access to the lake involves multi-day hikes through the mountain terrain with overnight stays at yurt camps positioned along the route. Visitors should prepare for uneven ground, changing weather conditions, and the effects of high altitude on their bodies.

The lake is held back by a natural rock dam, and its water does not flow out over the top: it seeps under the dam and emerges as a stream feeding the Karakol River. The first outsider known to have reached it, the Russian traveller Putimtsoff in 1811, noted rocks of different colours in the water and furious winds around the shore.