A reticulated python curled up on a rock in a rainforest

Determining the biggest snake in the world depends on whether you're measuring by length or weight. There are huge species in the python and boa families. © Mark_Kostich/ Shutterstock 

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What is the biggest snake in the world?

Snakes can grow to colossal sizes, although some reports have long been exaggerated.

The largest snakes in the world belong to the python and boa families. Which family contains the biggest depends on whether you are measuring these reptiles by weight or length.

While man-eating snakes are exceptionally rare (although it has been known to happen), there are some truly huge reptile species slithering about on our planet.

What is the longest snake in the world?

A reticulated python curled up on a road, rearing up slightly

Reticulated pythons are the longest snakes in the world. They are native to southeast Asia © Opayaza12/ Shutterstock 

The reticulated python (Malayopython reticulatus) is the longest snake in the world, regularly reaching over 6.25 metres in length. It is the longest of the 39 species in the family Pythonidae. 

The longest reticulated python ever recorded was found in 1912 and measured in at a staggering 10 metres - that's more than half the length of a bowling lane and makes this snake longer than a giraffe is tall.

Reticulated pythons live in southeast Asia and while they are typically found in rainforests, woodland and grasslands, their habitat preference seems to depend on their location. In Myanmar, these non-venomous snakes have only been found in pristine forest, whereas in Singapore, Indonesia and Malaysian Borneo they've also been recorded in sewers. 

A newly hatched reticulated python slithers over its egg

Reticulated pythons hatch at about 60 centimetres long, but grow to huge sizes in their lifetime. © Ralfa Padantya/ Shutterstock 

Reticulated pythons are known to climb trees by firmly wrapping their bodies around the trunks and using muscular upward force.

The longest and heaviest snake to ever be held in captivity was a female reticulated python called Medusa. Held in the USA, Medusa reached 7.67 metres long and weighed 158.8 kilograms.

Green anacondas (Eunectes murinus) are also exceptionally long snakes. But they have also been subject to exaggerated length measurements in the past, with snakes of over 24 metres allegedly sighted. In reality, the green anaconda rarely exceeds 6.25 metres.

The longest venomous snake

A king cobra in a defensive posture with the front of it's body raised and neck ribs slightly flattened into a hood

King cobras are the longest venomous snakes in the world. This one is showing off its length in a raised, defensive posture. © Jolly Therattil/ Shutterstock 

The king cobra (Ophiophagus hannah) is the world's longest venomous snake.

In 1937, a 5.54-metre-long king cobra was found in Negeri Sembilan state on the Malay Peninsula. Captured and kept at London Zoo, it eventually grew to 5.71 metres. But this huge snake was killed at the outbreak of the Second World War, to avoid putting the public in danger should the zoo be bombed and the snake escape.

Over five metres is unusual for king cobras, although even their average length of 3.7-4.6 metres makes them large animals.

These snakes best show off their length when they're feeling defensive or need to see above tall grass or bushes.

They will raise the front of their body up to about one metre off the ground and can even chase threats while in this posture. As an additional scare tactic, they will hiss and flatten their neck ribs into a hood, giving them the classic cobra shape.

A black and white photo of a Museum worker holding a dead king cobra specimen

A Museum worker holds a king cobra specimen in the 1930s. It is thought that the specimen may have just arrived at the Museum when this photo was taken. Discover more about our amphibian and reptile collections.  

These snakes generally prefer to flee than fight, however.

King cobras are found in south and southeast Asia in a variety of habitats including forests, mangrove swamps and some agricultural land with remnants of woodland. They're also competent swimmers.

However, they are generally uncommon in any of the areas they inhabit, with the exception of some forested areas in Thailand.

King cobras are listed as Vulnerable by the International Union for Conservation of Nature. In parts of their range, they have faced population declines of over 80% in 10 years due to habitat loss and exploitation, such as being harvested for its skin, food and medicinal purposes.

Find out more about the global trade in wild animals

The longest sea snake

A colour illustration of a yellow sea snake

Yellow sea snakes are thought to be the longest sea snake species in the world © Biodiversity Heritage Library via Flickr (CC BY 2.0)

Growing up to 2.75 metres long, the yellow sea snake (Hydrophis spiralis) is the longest species of sea snake. Most specimens that have been collected are less than two metres long, however.

The yellow sea snake lives in the northern Indian Ocean and around parts of southeast Asia, as well as being seen near New Caledonia in the southwest Pacific Ocean.

The paddle-like tail of a yellow-bellied sea snake

All sea snakes, including the yellow sea snake, have paddle-like tails to help them move through the water. This is the tail of a yellow-bellied sea snake. © NickEvansKZN/ Shutterstock 

Relatively little is known about these sea snakes. There have been records of the species at up to 50 metres below the surface and it is generally found over muddy sandy bottoms, feeding on eels.

What is the heaviest snake in the world?

A green anaconda curled up on a tree trunk in a rainforest

Green anacondas are the heaviest snakes in the world. Their size has been exaggerated in the past, however. © LABETAA Andre/ Shutterstock 

Green anacondas are the heaviest snakes in the world. The heaviest anaconda ever recorded was 227 kilograms. This massive snake was 8.43 metres long, with a girth of 1.11 metres.

While the reticulated python is longer, it's also slender. Anacondas are bulky. It's estimated that a 5.2-metre-long anaconda would weigh about the same as a 7.3-metre-long reticulated python. 

A close up of an anaconda's head

Anacondas spend most of their time in water, and have eyes and nostrils on the top of their head © Danny Ye/ Shutterstock  

Green anacondas are non-venomous, solitary and found in South America and Trinidad. They spend most of their time in water, usually in swamps, marshes, slow streams and rivers. Because of this, the nostrils and eyes have evolved to be on top of the head, rather than to the sides, so that the snake can breathe and see prey and predators above water while its large body is kept submerged.

These snakes have a varied diet, from turtles and fish to peccaries, deer, capybaras (the world's largest rodent), and even jaguars on rare occasions. Anacondas belong to the boa family and use their long, muscular bodies to constrict their prey

A black and white photo of six Bronx Zoo workers in 1912. Five of them are holding up a live anaconda

A large anaconda is lifted out of a case on arrival at the New York Zoological Park (now the Bronx Zoo) in 1912 . Image: Internet Archive Book Images via Flickr

Although 'anaconda' is often used to refer to green anacondas, there are actually three other species that are all marginally smaller: the Bolivian anaconda (Eunectes beniensis), dark-spotted anaconda (Eunectes deschauenseei) and the yellow anaconda (Eunectes notaeus). They are all found in South America.

The heaviest venomous snake

An eastern diamondback rattlesnake curled up in a defensive posture

Eastern diamondback rattlesnakes are heaviest venomous snakes in the world © Chase D'animulls/ Shutterstock 

The eastern diamondback (Crotalus adamanteus) is a rattlesnake and thought to be the world's heaviest venomous snake, with a particularly massive 2.56-metre individual tipping the scales at 15 kilograms.

Typically, the eastern diamondback reaches 5.5-6.8 kilograms and 1.5-1.8 metres long, however.

Found in southeastern USA, this snake prefers flatwoods, coastal forests and scrubland habitats. It isn't often found in wet areas, although it's a confident swimmer, occasionally seen in swamps and between barrier reefs. 

The tail rattle of an eastern diamondback rattlesnake

Rattlesnakes are named for the rattle at the ends of their tails. This structure is made up of interlocking hollow segments. The snakes rapidly vibrate their tails, creating a rattling noise and used as a warning to potential predators. © Chase D'animulls/ Shutterstock 

Adult eastern diamondbacks dine on small mammals, such as rabbits and squirrels, and small birds, while the young eat rats and mice. They strike their prey with a venom-filled bite, before letting it crawl away and die, at which point the snake eats it.

The Gaboon viper (Bitis gabonica), is another large snake, but it doesn't get quite as heavy as the eastern diamondback rattlesnake. A particularly long individual of 1.83 metres did weigh in at 11.34 kilograms, however.  

A preserved head of a Gaboon viper with its long fangs exposed

Gaboon vipers are the snake species with the longest fangs

While they aren't generally as heavy as the eastern diamondback, Gaboon vipers have fangs which are the longest of any snake at 55 millimetres. They also have the highest yield of venom, carrying up to 600 milligrams at a time.

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