The giant freshwater stingray (Urogymnus polylepis) is the world’s largest recorded fish that lives in fresh or brackish water. A female caught, documented, tagged, and released in Cambodia’s Mekong River weighed 300 kilograms (661 pounds) and measured 3.98 meters (13 feet) long, including its tail. Its disc was about 2.2 meters (7 feet 3 inches) wide.
There is an important qualification: the beluga sturgeon can grow larger overall, but it migrates between the sea and freshwater. That makes it anadromous rather than an exclusively freshwater fish.
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The giant freshwater stingray holds the freshwater record
The current record-holder is the giant freshwater stingray, also called the giant freshwater whipray. Guinness World Records recognizes a 300-kilogram female caught in Cambodia’s Mekong River on June 13, 2022, as the largest recorded freshwater fish.
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| Measurement | Record stingray |
|---|---|
| Species | Urogymnus polylepis |
| Common names | Giant freshwater stingray; giant freshwater whipray |
| Weight | 300 kg (661 lb) |
| Total length | 3.98 m (13 ft), including the tail |
| Disc width | About 2.2 m (7 ft 3 in) |
| Location | Mekong River near Koh Preah, Cambodia |
| Date recorded | June 13, 2022 |
What does “freshwater fish” mean?
The apparent disagreement between different sources usually comes down to the definition of freshwater fish. The giant freshwater stingray can live in large rivers and estuaries and tolerates both freshwater and brackish water. In everyday use, it is considered a freshwater fish because it spends its life in river and estuarine systems rather than undertaking a regular ocean migration.
For a careful comparison, the most defensible wording is:
The giant freshwater stingray is the largest reliably recorded fish that lives exclusively in freshwater or brackish environments.
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That wording avoids claiming that no larger fish has ever existed or that every large fish reported from a river meets exactly the same biological definition. It also explains why the beluga sturgeon sometimes appears as the answer.
Why the beluga sturgeon is not the same kind of record-holder
The beluga sturgeon (Huso huso) can grow considerably larger than the documented 300-kilogram stingray. However, beluga sturgeon are anadromous: they spend part of their lives in the sea and return to freshwater rivers to spawn.
So both of these statements can be correct:
- The giant freshwater stingray is the largest recorded fish that lives exclusively in freshwater or brackish environments.
- The beluga sturgeon is a larger fish overall, but it is not exclusively freshwater because it migrates between saltwater and freshwater.
This is why record references may classify the beluga sturgeon as the largest anadromous fish while listing the giant freshwater stingray as the largest freshwater fish.
If you want to compare this record with other species, a freshwater fish field guide can help distinguish permanently river-dwelling species from fish that merely enter freshwater during part of their life cycle.
What does the giant freshwater stingray look like?
Like other stingrays, this species has a broad, flattened body called a disc and a long, whip-like tail. Its body is supported by cartilage rather than the bony skeleton found in most familiar freshwater fish. A venomous spine on the tail is used defensively; it is not a tool the animal uses to hunt people.
The record animal’s enormous disc was wider than many adult humans are tall. Its nearly 4-meter total length was partly due to its tail, so the disc width and total length describe different aspects of its size. For rays, body width is often especially useful because the flattened disc contains much of the animal’s mass.
Older scientific literature may use the name Himantura chaophraya for this species. Urogymnus polylepis is the currently accepted scientific name in the research summarized for this record.
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Where do giant freshwater stingrays live?
Giant freshwater stingrays inhabit large rivers and estuaries in Southeast Asia and parts of Borneo. They need extensive aquatic habitat and are associated with major river systems, including the Mekong.
These are not ordinary pond or aquarium fish. Their size, movements, habitat requirements, and defensive tail spine make them unsuitable for private ownership. The record animal’s acoustic tag allowed researchers to learn more about how it moved through the river after release—information that is difficult to obtain for a large, elusive fish.
Other giant freshwater-fish contenders
The stingray is the current recorded winner, but several other species are important to the comparison.
Mekong giant catfish
The Mekong giant catfish (Pangasianodon gigas) is one of the largest true freshwater bony fish. A specimen caught in Thailand in 2005 weighed 293 kilograms and measured approximately 2.7 meters. It held the freshwater record before the 300-kilogram Cambodian stingray was documented.
Unlike a stingray, it has the familiar body plan of a bony fish, with a streamlined body and fins rather than a broad ray-like disc. It is also critically vulnerable to changes in the Mekong and is rarely encountered at its former abundance.
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Arapaima (Arapaima gigas) are among the longest and largest scaled freshwater fish. Reports of individuals exceeding 4 meters make them impressive contenders for length, but they generally weigh less than the record stingray. Length and weight do not always produce the same “largest” species: a long, slender fish may weigh less than a shorter, much heavier animal.
White sturgeon
White sturgeon can reach extraordinary sizes and are often included in lists of the world’s largest freshwater fish. Comparisons can be difficult because sturgeon records may involve historical reports, different definitions of freshwater habitat, or fish that spend part of their lives in brackish or marine water.
Beluga sturgeon
Beluga sturgeon exceed the giant freshwater stingray in some reported size estimates, but their anadromous life cycle is the key distinction. They should be described as larger migratory fish, not as the largest exclusively freshwater fish.
Chinese paddlefish
The extinct Chinese paddlefish was once discussed as another giant river-fish contender. Historical accounts included very large estimates, but the species was declared extinct after decades without reliable confirmation. It should not be presented as a living alternative to the current record-holder.
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Why the record matters for conservation
A giant freshwater stingray is not just a surprising entry in a size ranking. Its record shows how much remains to be learned about the Mekong’s largest animals—and how vulnerable those animals are when rivers are altered.
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The species is considered endangered. Its vulnerability is linked to several traits and pressures:
- Large body size: Very large animals generally need substantial food supplies and extensive habitat.
- Slow growth and late maturity: Populations may recover slowly when adult fish are removed.
- Fishing pressure: Large individuals are particularly noticeable and may be more likely to be caught.
- Dams and habitat fragmentation: Barriers can interfere with movement through the river system.
- Changed water flows: Altered hydrology can affect feeding, breeding, and seasonal movements.
- Water-quality degradation: Pollution and sediment changes can damage the habitats on which river megafish depend.
Large river fish are especially difficult to protect because their ranges may cross multiple jurisdictions and because their movements connect different parts of a river. Main-stem dams, fragmented habitat, and changes in natural flow patterns can affect animals far beyond the immediate construction site.
The 2022 fish was tagged and released, allowing researchers to study its movements rather than removing it from the Mekong. That makes the record a useful example of how documentation and conservation research can work together.
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How to compare giant freshwater fish fairly
When you see a claim about the “biggest” freshwater fish, check four details:
- Is the species exclusively freshwater? Anadromous fish such as beluga sturgeon may enter rivers but also live in the sea.
- Is the number from a measured specimen? A weighed, documented fish is more reliable than an unverified historical estimate.
- Is the comparison based on weight or length? The longest species is not necessarily the heaviest.
- Is the species still living? Extinct fish and historical reports should not be mixed casually with current records.
Using those standards, the giant freshwater stingray is the best current answer: it is the heaviest reliably documented fish meeting the practical freshwater definition, with a verified 300-kilogram specimen from the Mekong.
Frequently Asked Questions
Is the giant freshwater stingray bigger than the Mekong giant catfish?
The documented record stingray was heavier. It weighed 300 kilograms, while the well-known 2005 Mekong giant catfish record weighed 293 kilograms. The two species have different body shapes, so length and weight should not be treated as interchangeable.
Is a beluga sturgeon a freshwater fish?
Beluga sturgeon use freshwater rivers, but they are anadromous: they migrate between freshwater and the sea. That is why they can be larger overall while not qualifying as the largest exclusively freshwater fish.
Are giant freshwater stingrays dangerous?
They have a venomous defensive spine on the tail and should never be approached or handled. The record animal was handled by trained researchers during a scientific tagging operation, then released.
Can giant freshwater stingrays be kept as pets?
No. Their enormous adult size, specialized river habitat, conservation status, and defensive spine make them inappropriate for private pet ownership. The record species should be viewed as a wild conservation subject, not an aquarium animal.
The Bottom Line
Bottom line: The giant freshwater stingray (Urogymnus polylepis) is the world’s largest recorded fish that lives in fresh or brackish water. The record female from Cambodia’s Mekong River weighed 300 kilograms and measured nearly 4 meters long. The beluga sturgeon can be larger, but it migrates between the sea and freshwater, so it belongs in a different category.
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