What is the heaviest animal on record? The heaviest blue whale on record was a female caught in the Southern Ocean in 1947. She was 27.6 meters long and about 190 tonnes. The longest Antarctic whale carefully measured was 29.5 meters and 163 tonnes. A typical grown whale weighs between 72 and 135 tonnes, much less than the record-holders. Whalers took 350,000 to 360,000 blue whales in the first half of the 20th century. The International Whaling Commission banned all blue whale hunting in 1966; as of November 2026, blue whales are listed as endangered, and their numbers are slowly rising. A newborn blue whale calf is already about 23 to 25 feet long.

A blue whale's heart is the biggest known in any animal. One stranded North Atlantic blue whale's heart weighed 180 kg. Its brain weighed only about 3.6 kg, though the whole whale was about 50.9 tonnes. The sperm whale has the largest brain on Earth, more than five times heavier than a human's; a blue whale lives about 80 to 90 years. When it lunges to feed, it can take in about 220 tonnes of water at once. It squeezes the water out through its baleen plates with its throat pouch and tongue, and swallows the krill left behind. It can eat about 4 tons of krill in a single day.

In 2023 scientists described Perucetus colossus, a whale from the middle Eocene of Peru. Its skeleton weight is thought to be greater than that of any known mammal or aquatic vertebrate. To judge how heavy it was, the team compared skeleton weight with whole-body weight in many living animals. Applying that ratio gave a body weight that makes it a contender for the heaviest animal on record. As of November 2026, one guess ranges from 85 to 340 tonnes, averaging about 180 tonnes. That range overlaps the heaviest blue whales (190 to 200 tonnes) and is still argued. Perucetus was probably much shorter than a blue whale. Length guesses run from about 15 to 20 meters, while the longest confirmed blue whales are about 30 meters.

Land giants make a different kind of argument. As of November 2026, Argentinosaurus is known only from fragmentary remains. It was one of the largest land animals of all time, put at 30 to 35 meters long and 65 to 80 tonnes. Paraceratherium was one of the largest land mammals known. It stood about 4.8 meters at the shoulder and was about 7.4 meters long. Its weight is put at 15 to 20 tonnes. The largest elephant on record was a grown male African savanna elephant. It weighed about 24,000 pounds (10,886 kg) and stood 13 feet (3.96 meters) at the shoulder, as of November 2026. Elephants are the heaviest living land animals, with no heavier animal on land today.

Fish records are unsettled. As of November 2026, whale shark record lengths are not settled. Animal Diversity Web lists 20 meters, while Wikipedia says the largest total length is uncertain due to a lack of detailed documentation. Leedsichthys, a Jurassic fish, was the largest ray-finned fish known. Older estimates were larger, but recent research lowered the biggest to about 16.5 meters. Ocean sunfish were once thought to be the heaviest bony fish. That title belongs to a closely related species. A young ocean sunfish at the Monterey Bay Aquarium grew from 26 kg to 399 kg in 15 months. A mother ocean sunfish can produce up to 300 million eggs at a time, more than any other known vertebrate.

Weight in crocodiles rises roughly with the cube of length. A 6-meter saltwater crocodile weighs more than twice as much as a 5-meter one. As of November 2026, male saltwater crocodiles can weigh 1,000 to 1,500 kg and reach about 6 meters, rarely more than 6.3 meters. How big the biggest anacondas get is disputed. Records of 10 to 12 meter snakes weighing up to 250 kg exist, but one measured snake was 7.5 meters and thought to weigh 136 to 180 kg. The green anaconda is slightly shorter than the reticulated python but far bulkier, so the anaconda is the heavier snake. Komodo dragons live on a few Indonesian islands.

Small giants are measured too. As of November 2026, Japanese spider crabs have the greatest leg span of any known arthropod, up to 3.7 meters. They weigh up to 19 kg, second in weight among arthropods only to the American lobster. The giant weta of New Zealand has eleven species. One captive weta reached about 70 g, which is heavier than a sparrow. As of November 2026, coconut crabs are the largest living land-dwelling arthropods, weighing up to 4.1 kg. Goliath beetles live in the tropical forests of Africa and are among the largest insects on Earth.

Words to know

• tonnes: metric tons
• contender: strong rival
• fragmentary: in pieces
• baleen: whale strainer