The following list ranks the world’s five deepest lakes by a single, consistent metric: maximum depth in metres — the single deepest surveyed sounding for open lakes or the best‑supported geophysical estimate for subglacial bodies. That metric measures the greatest water column depth recorded or inferred within each basin and does not account for area or volume. Scope decisions important to this list: the Caspian Sea is treated as an inland lake (endorheic basin) for depth ranking, and Lake Vostok is included even though its depth is an inferred geophysical estimate rather than a direct sounding. Where recent bathymetric revisions exist (for example, O’Higgins / San Martín), the revised values are used.

Quick Comparison

Rank	Lake	Location	Maximum depth (m)
1	Lake Baikal	Southern Siberia, Russia	1,642 m
2	Lake Tanganyika	East African Rift (Burundi, DRC, Tanzania, Zambia)	1,470 m
3	Caspian Sea	Between Europe and Asia (Russia, Kazakhstan, Turkmenistan, Iran, Azerbaijan)	1,025 m
4	Lake Vostok (subglacial)	East Antarctica (beneath the Antarctic ice sheet)	~900 m
5	O’Higgins / San Martín Lake	Patagonia — Chile / Argentina border	799 m

#5 — O’Higgins / San Martín Lake

Location: Patagonia — border Chile / Argentina.

Ranking value: 799 m

Relevant year: 2023 (bathymetric revision reported Dec 2023).

O’Higgins / San Martín sits at the spine of southern South America and is the deepest lake in the Americas under the maximum‑depth metric used here. A December 2023 bathymetric revision lowered the best‑supported maximum to 799 m, replacing earlier figures used on some older lists. The lake receives direct meltwater from the Southern Patagonian Ice Field; suspended glacial sediments (“rock flour”) give it a characteristic milky blue color. Its depth is notable both for continental ranking and for the dynamic glacial and tectonic environment that shapes Patagonia’s fjords and deep basins.

Interesting fact: It is the deepest lake in the Americas and is fed directly by glaciers from the Southern Patagonian Ice Field, giving its milky blue color from glacial “rock flour.”

#4 — Lake Vostok (subglacial)

Location: East Antarctica (beneath ~3.5–4 km of ice, near Vostok Station).

Ranking value: ~900 m (geophysical estimate; not directly sounded)

Relevant year: Estimates derived from airborne geophysical and aerogravity/radar studies conducted from the late 1990s into the 2000s (summarized in early‑2000s reviews).

Lake Vostok is a subglacial freshwater lake trapped beneath several kilometres of Antarctic ice. Its maximum depth is an inferred value derived from geophysical surveys (radar, gravity, seismic), not from direct in‑water soundings; therefore the reported ~900 m is an estimate rather than a measured sounding. Vostok has drawn scientific attention because it has been isolated from the atmosphere for long periods, and while refrozen lake water has been sampled in ice cores, the lake’s main water column has not been accessed in situ without risk of contamination. Its inclusion here reflects the ranking rule that geophysically inferred maxima for subglacial lakes are eligible.

Interesting fact: Vostok is a subglacial freshwater lake isolated beneath the Antarctic ice sheet; its water was indirectly sampled via refrozen lake water in the Vostok ice core but the lake water column has not been directly sampled in situ without contamination.

#3 — Caspian Sea

Location: Between Europe and Asia — bounded by Russia, Kazakhstan, Turkmenistan, Iran, Azerbaijan.

Ranking value: 1,025 m

Relevant year: Bathymetric consensus reflected in regional basin studies from the 1990s–2010s.

Though commonly called a “sea,” the Caspian is an endorheic (closed) inland basin and for depth ranking purposes it is treated as a lake. The southern basin reaches roughly 1,025 m, making it one of the deepest enclosed water bodies on Earth. The Caspian’s depth and isolation have produced distinctive ecological and economic systems — including endemic fauna such as the Caspian seal and extensive sturgeon fisheries that have supported long‑distance caviar trade for centuries. Its large, deep basins also make the Caspian an important subject for hydrographic and environmental study across multiple national jurisdictions.

Interesting fact: Although called a “sea,” the Caspian is an endorheic (closed) basin and its deepest point (southern basin) reaches ~1,025 m; it supports unique fauna including the Caspian seal and major sturgeon fisheries.

#2 — Lake Tanganyika

Location: East African Rift — borders Burundi, Democratic Republic of the Congo, Tanzania, Zambia.

Ranking value: 1,470 m

Relevant year: Classic bathymetric compilations and FAO basin data (citations from 1970s onward, consolidated in FAO publications).

Lake Tanganyika is the second‑deepest lake on Earth and the deepest freshwater lake in Africa. Its depth (1,470 m) results from its position within the East African Rift — a major tectonic graben that has produced steep fault‑bounded basins. The lake supports extraordinary endemic biodiversity, most famously hundreds of species of cichlid fishes that evolved in isolation across complex habitats. Tanganyika’s deep waters are largely anoxic below roughly 200 m, a chemical stratification that strongly shapes its biology and fisheries. The lake’s depth and rift origin make it a classic subject in studies of evolution, ecology, and continental tectonics.

Interesting fact: Tanganyika is the deepest freshwater lake in Africa and hosts enormous endemic biodiversity (hundreds of cichlid species); below ~200 m the lake is essentially anoxic.

#1 — Lake Baikal

Location: Southern Siberia, Russia (Irkutsk Oblast & Buryatia).

Ranking value: 1,642 m

Relevant year: Computer‑based bathymetric compilation published 2006 (consolidation of hydrographic surveys).

Lake Baikal is the deepest lake in the world under the maximum‑depth metric, with a widely cited bathymetric maximum of 1,642 m from a comprehensive 2006 compilation. Baikal is also the planet’s largest freshwater lake by volume, containing an outsized share — roughly one fifth — of the world’s unfrozen surface freshwater. Its great depth, ancient age, and isolation have produced high levels of endemism (including the freshwater seal, the nerpa). Baikal’s geology reflects active rifting and faulting in southern Siberia, and its bathymetry has been a subject of detailed hydrographic mapping and scientific study.

Interesting fact: Baikal is the world’s deepest lake and the largest freshwater lake by volume (contains roughly ~20%–23% of the planet’s surface unfrozen fresh water); it also hosts the only exclusively freshwater seal (the nerpa).

How We Ranked Them

Metric used: Maximum depth — the single greatest surveyed or geophysically‑inferred water depth in metres. For open lakes this is the deepest reliable sounding; for subglacial lakes it is the best‑supported geophysical estimate when direct in‑water soundings are not available.

We compiled authoritative, domain‑specific bathymetric and geophysical sources and applied the metric consistently to all candidate basins. Important scope choices include treating the Caspian as an inland lake (endorheic sea) for depth ranking and allowing geophysically inferred maxima (e.g., Lake Vostok) to appear on the list because direct sounding is not possible under ice. We used recent, peer‑reviewed bathymetric revisions where available — for example, the 2023 revision for O’Higgins / San Martín — and accepted widely cited compilations for large basins such as Baikal and Tanganyika.

Significant uncertainties and limitations: Lake Vostok’s depth is an inferred geophysical estimate (~900 m) rather than a direct sounding, and subglacial measurements carry extra uncertainty because they rely on radar, gravity, and seismic models. Historical or secondary sources sometimes report slightly different values (for example, older Baikal figures near 1,620 m); where a specialist bathymetric compilation exists, we used that primary compilation. Bathymetric data are also sensitive to survey method, resolution, and, for surface‑connected lakes, natural water‑level change; those factors explain some discrepancies between older and newer numbers.

Frequently Asked Questions

Why is the Caspian Sea listed as a lake?

For the purposes of depth ranking the Caspian is treated as an inland lake because it is an endorheic basin (a closed inland body of water with no oceanic outlet). That classification is standard in hydrographic and basin studies when comparing maximum depths among enclosed bodies of water.

Is Lake Vostok’s depth measured directly?

No. Lake Vostok’s reported depth (~900 m) is a geophysical estimate based on airborne radar, gravity and seismic surveys. The lake lies beneath several kilometres of ice, and its main water column has not been accessed directly in situ without contamination risk; only refrozen lake water has been sampled within ice cores.

Why do some sources give different depths for the same lake?

Differences arise from survey method, data resolution, and revisions to bathymetric compilations. Older surveys, lower‑resolution data, or reliance on secondary summaries can produce variant figures. For some lakes, recent re‑surveying or reanalysis of geophysical data has led to updated maximum depths (for example, O’Higgins / San Martín was revised to 799 m in 2023).

Can lake depths change over time?

Reported maximum depths can change due to improved measurement techniques or revision of bathymetric compilations. Actual basin depths may also be affected by tectonics, sedimentation, or long‑term water‑level shifts, but most short‑term changes in reported depth reflect measurement and analysis updates rather than rapid basin deepening.

Sources

• Computer‑based bathymetric map of Lake Baikal — primary bathymetric compilation reporting Baikal’s consolidated maximum depth (1,642 m).
• Lake Tanganyika Research | Background | General Features — FAO basin data and compilations citing Tanganyika’s maximum depth (1,470 m) and lake characteristics.
• Regional Framework Planning for Lake Tanganyika Fisheries Management — supporting FAO technical material on Tanganyika’s depth and ecology.
• CASPIAN SEA i. GEOGRAPHY – Encyclopaedia Iranica — regional summary reporting the Caspian’s southern‑basin maximum depth (~1,025 m) and geographic context.
• 3.16 Caspian Sea — JRC/interregional publication with basin bathymetry details used in depth consensus for the Caspian.
• O’Higgins/San Martín Lake – Wikipedia — summary entry reflecting the 2023 bathymetric revision to 799 m and background on the lake’s glacial feed and color.
• (PDF) Subglacial Lake Ellsworth: a candidate for in situ exploration in West Antarctica. Geophys Res Lett 31(23):L23403, 10.1029/2004GL021477 — representative geophysical literature on Antarctic subglacial lake surveying and inference methods cited in summaries of Lake Vostok’s depth.
• List of lakes by depth — consolidated list of global lake depths used for cross‑checking ranks and values.
• Largest freshwater lake by volume | Guinness World Records — supporting reference for Baikal’s status as the largest freshwater lake by volume.

Last Updated

September 2026