The oldest lake in the world is usually given as Lake Baikal in Siberia, Russia, which has held water for 25 to 30 million years. Two rivals claim to be older, but each comes with a catch: Lake Zaysan in Kazakhstan may date from the Cretaceous, at least 66 million years ago, yet its age is uncertain and a dam has turned it into part of a reservoir; Lake Maracaibo in Venezuela formed 20 to 36 million years ago but is now a brackish bay open to the sea. Which lake “wins” depends on what you count as a lake’s age, so so the measuring rules come first and the ranking second.
What “Ancient Lake” Means and Who Keeps the List
Most lakes are short-lived. Rivers carry sediment into them, and within thousands of years they fill up, drain or dry out; most of the planet’s inland water bodies are less than 18,000 years old, and the North American Great Lakes date only from the end of the last ice age, about 14,000 years ago. Limnologists therefore use the term ancient lake for a lake that has carried water continuously for more than one million years. Only about 20 qualify.
The ranking used here comes from the table in Wikipedia’s Ancient lake article, which cites a database of the world’s 20 ancient lakes compiled in 2016 by Christopher Free and published on a Rutgers University website. The table gives an age, often as a range, for each lake, and leaves out the many subglacial lakes of Antarctica whose ages are still unknown, apart from Lake Vostok.
The word “continuously” is where the arguments start. A lake’s age can be measured in at least three ways, and they rarely agree:
- Age of the basin. When did the faults, crater or depression that holds the lake first form? This gives the oldest numbers.
- Age of the oldest lake sediments. Drilling into the lake floor shows how long water has been laying down mud, but cores rarely reach the bottom of the pile.
- Age of the present lake. Has the basin held water without drying out or turning into something else, such as a bay or a reservoir? This gives the youngest and strictest numbers.
One lake can carry very different ages depending on which question a source answers. That is why the table below shows ranges, and why several well-known lakes look younger here than in their own encyclopedia articles.
Ten Oldest Lakes, Ranked by Minimum Age
Lakes are ranked by the lower bound of the age the table gives, since that is the age the evidence supports at a minimum; ties are broken by the upper bound.
| Rank | Lake | Country or countries | Age (million years) |
|---|---|---|---|
| 1 | Lake Zaysan | Kazakhstan | 65+ |
| 2 | Lake Baikal | Russia | 25+ (25–30) |
| 3 | Issyk-Kul | Kyrgyzstan | 25 |
| 4 | Lake Maracaibo | Venezuela | 20+ |
| 5 | Lake Vostok | Antarctica | 15–35 |
| 6= | Aral Sea | Kazakhstan, Uzbekistan | 5.5 |
| 6= | Karakul | Tajikistan | 5.5 |
| 8 | Caspian Sea | Azerbaijan, Iran, Kazakhstan, Russia, Turkmenistan | 5–25 |
| 9 | Lake Biwa | Japan | 5–6 |
| 10 | Tule Lake | United States | 3–15 |
Lake Tanganyika (3–6 million years) and Lake Titicaca (3) come next, with Lake Malawi (2–5) a few places lower, even though each has a strong case to be older, as the last section explains.
Lake Zaysan’s Cretaceous Claim and the Bukhtarma Dam
Zaysan lies in East Kazakhstan Region at 420 m above sea level, in a hollow between the Altai and Tarbagatai mountains. It is about 105 km long, is fed from the east by the Kara Irtysh and drains through the Irtysh. Its name comes from the Mongolian Zaisan nuur, “Noble Lake”. Some geological studies of the Zaysan Basin support an exceptionally old age, possibly from the Cretaceous, more than 66 million years ago and most likely about 70 million; a 2011 paper by B. F. Dorfman called it the only surviving Cretaceous lake. A study of dinosaur eggshell and the Cretaceous–Paleogene boundary in the basin has also been cited.
Two problems keep Zaysan from being the accepted record holder. First, its exact age is debated, and a clear dating has proved hard to find. Second, the lake had been drying until the Bukhtarma Dam was built downstream on the Irtysh. The reservoir raised Zaysan about 6 m above its natural level and roughly doubled its area, from about 1,800 km² to 3,500 km² or more, so some sources now treat it as part of an artificial reservoir rather than a natural lake.
Lake Baikal: 25–30 Million Years and a 6.7-Million-Year Core
Baikal is the lake most sources, including UNESCO, name as the oldest, because its age rests on clear evidence and nobody disputes that it is still a natural, freshwater lake. It fills a basin of the Baikal Rift Zone in southern Siberia, where the two sides of the crust are still separating by about 4 mm a year. That steady subsidence has kept it alive: the active rift sinks the basin faster than rivers can fill it, even though about 7 km of sediment already lies beneath the water.
Baikal is also unusual among large lakes at high latitude because ice-age glaciers never scoured out its sediments. Russian, American and Japanese teams drilled cores there in the 1990s that preserve a continuous climate record covering the last 6.7 million years. Its long isolation shows in its wildlife: the Baikal seal, or nerpa, lives nowhere else; more than half of its fewer than 65 native fish species are endemic; and about half of its 400-plus diatom species are found only there. Because Baikal is also the deepest lake on Earth, it heads our separate ranking of the deepest lakes in the world too.
Maracaibo, Vostok and Issyk-Kul: Old Basins With Caveats
Lake Maracaibo formed about 36 million years ago, when faults collapsed as the Andes rose in the late Eocene, and more than 5 km of sediment has built up on its bedrock since. At 13,512 km² it would be South America’s largest lake if counted as one. But it now connects to the Gulf of Venezuela through a narrow strait, its water is brackish, and sea and fresh water have alternated many times in its history, so many geographers classify it as an estuary or bay. The table lists it at “20+” million years with that warning; our Lake Maracaibo guide covers its oil fields and Catatumbo lightning.
Lake Vostok, buried about 4,000 m under the East Antarctic Ice Sheet, gets a wide range of 15 to 35 million years in the table; it is known mainly from radar, seismic soundings and a single borehole. Its overlying ice preserves roughly 400,000 years of climate history, and the water beneath may have been isolated for 15 to 25 million years. Issyk-Kul in Kyrgyzstan, a saline lake 1,607 m up in the Tian Shan, is put at 25 million years by the table, though its own article gives no age, so the figure rests on that one listing.
The Caspian Sea shows how the three measuring methods split. Its southern basin is a remnant of the Paratethys Sea, and the sea as a whole is estimated to be about 30 million years old, but it only became landlocked about 5.5 million years ago, when uplift and falling sea level cut it off. The table’s wide range of 5 to 25 million years reflects that ambiguity: whether a cut-off sea counts as a lake from the day its basin formed or from the day it became landlocked.
Where Rival Dates Disagree: Tanganyika, Malawi, Titicaca and Ohrid
The lakes just outside the top ten show the gap between basin age and the strict “continuous lake” standard most clearly. Lake Tanganyika is listed at 3 to 6 million years in the table, yet its own article says its three basins formed at different times: the central basin 9 to 12 million years ago, the northern 7 to 8 million and the southern 2 to 4 million. Under the basin-age method, Tanganyika would rank sixth, just behind Lake Vostok.
Lake Malawi is put at 2 to 5 million years in the table and has often been estimated at just 1 to 2 million, but newer evidence suggests its basin began forming about 8.6 million years ago, with deep water appearing about 4.5 million years ago. Its level has also swung by almost 600 m; at times it shrank to one or two small, salty, alkaline lakes, and water chemistry like today’s returned only about 60,000 years ago.
Lake Titicaca, on the border of Peru and Bolivia, is listed at 3 million years, but sediments of an ancestral Lake Titicaca date from 18 to 14 million years ago. What happened between then and about 370,000 years ago is unknown, because those layers lie buried under the lake and have never been cored, so continuity cannot be proved. Karakul in Tajikistan, a lake inside a 52 km impact crater, is listed at 5.5 million years, while the Earth Impact Database puts the crater at under 5 million.
Lake Ohrid, shared by North Macedonia and Albania, is one of Europe’s oldest lakes, listed at 1.5 to 5 million years; its oldest lake sediments are Pliocene, possibly 3 to 5 million years old. It survives for the same reason as Baikal: the graben it sits in is still sinking, and its main inflows arrive through underground karst channels from Lake Prespa carrying little sediment. More than 200 endemic species live in it, and UNESCO listed the North Macedonian side in 1979 and the Albanian side in 2019. Ohrid, Baikal and Tanganyika all show the same rule: the lakes that last are the ones in active tectonic basins, the type described in our overview of the different types of lakes.