Largest Snakes in the World: Longest and Heaviest Species

How snake size is measured, and why records get exaggerated

Few animal records are as inflated as snake lengths. A live giant snake is almost impossible to stretch out straight, skins stretch by a fifth or more when removed and tanned, and people who see a big snake in the wild tend to overestimate it. Reliable records come from snakes measured with a tape, under anesthesia or soon after death, in front of witnesses.

Weight is easier to measure but varies hugely with recent meals and captivity: well-fed zoo snakes can be far heavier than any wild individual of the same length. For decades, the New York Zoological Society, now the Wildlife Conservation Society, offered a reward that eventually reached $50,000 for a live, healthy snake longer than 30 ft (9.1 m). It was never claimed.

1. Reticulated python: the longest snake

The reticulated python (Malayopython reticulatus) of South and Southeast Asia is the world’s longest snake. A study of more than 1,000 wild pythons in southern Sumatra found lengths of 1.5–6.5 m (5–21 ft) and weights of 1–75 kg (2–165 lb). Snakes over 6 m (20 ft) are rare.

The longest scientifically measured wild specimen, from Balikpapan in Indonesian Borneo, was 6.95 m (22 ft 10 in) long when measured under anesthesia; it weighed 59 kg (130 lb) after not eating for nearly three months. In captivity, a python named Medusa in Kansas City, Missouri, was recorded by Guinness World Records at 7.67 m (25 ft 2 in) and 158.8 kg (350 lb) in 2011. Reports of 9–10 m (30–33 ft) pythons have never been verified.

This slender, strong swimmer has reached many small islands. It is listed as Least Concern by the IUCN, but it is heavily harvested for its skin. It is one of very few snakes known to have killed and swallowed adult people, though such cases are rare.

2. Green anaconda: the heaviest snake

The green anaconda (Eunectes murinus) lives in swamps, slow rivers and flooded grasslands of northern South America, including the Amazon and Orinoco basins. It is a little shorter than the reticulated python but far bulkier: a 5.2 m (17 ft) anaconda is about as heavy as a 7.4 m (24 ft) reticulated python.

Females are much larger than males. Mature females typically reach up to about 5 m (16 ft), while males average around 3 m (10 ft), and typical adults weigh 30–80 kg (66–176 lb). Venezuelan biologist Jesús Rivas, who examined more than 900 anacondas, found the largest to be a female 5.21 m (17 ft 1 in) long weighing 97.5 kg (215 lb). Lengths up to about 6.3 m (21 ft) have been reported, but claims of 11–12 m (35–40 ft) anacondas have no physical evidence behind them.

The green anaconda is listed as Least Concern. A 2024 proposal to split off a separate northern green anaconda species has not been widely accepted.

3. Burmese python: a giant in Asia and in Florida

The Burmese python (Python bivittatus) is native to Southeast Asia, where it is listed as Vulnerable because of habitat loss and over-harvesting. Wild adults average about 3.7 m (12 ft), and individuals over 5 m (16 ft) are rare.

Ironically, the longest wild Burmese python on record was caught in the United States. Released or escaped pets have established a large invasive population in South Florida, including the Everglades, where they have been linked to severe declines of raccoons, opossums and rabbits. The record length, 5.79 m (19 ft), belongs to a female caught in Big Cypress National Preserve in July 2023 that weighed 57 kg (125 lb). A captive Burmese python named Baby weighed 182.8 kg (403 lb), much heavier than any wild snake ever measured. Read more in our guide to snakes in Florida.

4. African rock python: Africa’s largest snake

The Central African rock python (Python sebae) is Africa’s largest snake. Adults are usually about 3–3.5 m (10–11.5 ft) long, and specimens over 6 m (20 ft) are considered reliable; heavily built individuals can exceed 90 kg (200 lb). Its smaller relative, the Southern African rock python, lives farther south.

Rock pythons eat antelope, monkeys, birds and monitor lizards, and occasionally even young crocodiles such as the Nile crocodile. Unlike most snakes, the female coils around her eggs and guards the nest.

5. Australian scrub python: Australia’s longest snake

The Australian scrub python (Simalia kinghorni) lives in the rainforests and other forests of northern Queensland. It is the longest snake in Australia and one of the longest tree-climbing snakes in the world. Reliably measured animals reach about 5 m (16 ft), but they are slender, weighing roughly 25–28 kg (55–62 lb) at that length. Unusually, males grow larger than females.

6. Boa constrictor: big, but not a giant

The boa constrictor (Boa constrictor) of Central and South America is often imagined as enormous, but it is modest beside the pythons and anacondas. Adult females are usually 2.1–3 m (7–10 ft) long and males 1.8–2.4 m (6–8 ft). Exceptional females, mostly in captivity, reach about 4 m (13 ft), and large boas can weigh up to about 27 kg (60 lb).

7. King cobra: the longest venomous snake

The king cobra (Ophiophagus hannah) of South and Southeast Asia is the longest venomous snake. Adults are usually 3–4 m (10–13 ft), and the longest known specimens measured about 5.6–5.85 m (18.5–19.2 ft). It feeds mainly on other snakes and is the only snake known to build an above-ground nest for its eggs. In 2024, researchers proposed splitting it into four species.

The IUCN lists the king cobra as Vulnerable. King cobras usually avoid people, but their bite can be fatal; anyone bitten by any venomous snake should seek emergency medical help immediately.

8. Other long and heavy venomous snakes

The black mamba of sub-Saharan Africa is the second-longest venomous snake. Most adults are 2–3 m (6.5–10 ft), and lengths of about 4.3–4.5 m (14–15 ft) have been reported. The bushmaster of South America is the longest viper, at up to about 3.6 m (12 ft).

The heaviest venomous snakes are short, bulky vipers. A Gaboon viper of 1.8 m (5.9 ft) caught in 1973 weighed 11.3 kg (25 lb) with an empty stomach. The eastern diamondback rattlesnake of the southeastern US is the largest rattlesnake; most adults are 1.1–1.7 m (3.5–5.5 ft), and claims of 2.4 m (8 ft) giants are hard to confirm.

9. Eastern indigo snake: the longest native snake in the US

The eastern indigo snake (Drymarchon couperi) is a glossy, blue-black, nonvenomous snake found mainly in Florida and southeastern Georgia. It is the longest snake native to the United States, with a record of 2.8 m (9.2 ft). It is protected as a threatened species under the US Endangered Species Act.

Titanoboa and other giant snakes of the past

The largest snake known to science is extinct. Titanoboa cerrejonensis, described in 2009 from fossils found in the Cerrejón coal mines of northern Colombia, lived about 58–60 million years ago, some 6–8 million years after the dinosaurs disappeared. Based on its huge vertebrae, it is estimated to have reached about 12.8 m (42 ft) and roughly 730–1,135 kg (1,600–2,500 lb), and it probably ate mainly fish.

In 2024, scientists described Vasuki indicus from Kutch in western India, a snake of about 47 million years ago known from part of its backbone. Its estimated length of about 11–15 m (36–49 ft) may rival Titanoboa, but the estimate is very uncertain. For giant reptiles alive today, compare these snakes with how big crocodiles get.

Largest snakes compared

Giant snake myths and facts

Myth: anacondas grow to 40 feet. No anaconda anywhere near 12 m (40 ft) has ever been measured; the largest verified animals are around 5–6 m (16–20 ft).

Myth: a snake skin shows the snake’s true size. Skins stretch, often by 20 percent or more, so a skin can be much longer than the snake that wore it. The famous Pittsburgh zoo python Colossus was once credited with 8.7 m (28 ft 7 in), but its skeleton measured only 6.35 m (20 ft 10 in).

Myth: constrictors crush their prey’s bones. Pythons, boas and anacondas kill mainly by squeezing hard enough to stop blood flow, which quickly leads to cardiac arrest; crushing bones is not how they kill.