The largest extant animal, as well as the largest animal to ever exist, is the blue whale. The maximum recorded weight was 190 tonnes for a specimen measuring , whereas longer ones, up to , have been recorded but not weighed.Wood, Gerald The Guinness Book of Animal Facts and Feats (1983) It is estimated that this individual could have a mass of 250 tonnes or more. The longest non-colonial animal is the lion's mane jellyfish ().
While controversial, estimates for the weight of the sauropod Bruhathkayosaurus suggest it was around 110–170 tons, with the highest estimate being 240 tons, if scaled with Patagotitan, although actual fossil remains no longer exist, and that estimation is based on described dimensions in 1987. Similarly, the extinct whale Perucetus was initially estimated in 2023 to have a mass of . However, more recent studies suggest this whale was much smaller than previous estimates, with a 2024 study putting its weight at 60 to 113 tonnes, while a 2025 study further downsized its weight to 35 to 40 tonnes.
In April 2024, Ichthyotitan severnensis was established as a valid shastasaurid taxon and is considered both the largest marine reptile ever discovered and the largest macropredator ever discovered. The Lilstock specimen was estimated to be around whilst the Aust specimen was an even more impressive in length (however, the Aust specimen or 'Aust Colossus' may not belong to Ichthyotitan). While no weight estimates have been made as of yet, Ichthyotitan would have easily rivalled or surpassed the blue whale. The upper estimates of weight for these prehistoric animals would have easily rivaled or exceeded the largest rorquals and sauropods. However, an as-yet undescribed shastasaurid, informally referred to as 'Aust Colossus', may have exceeded Ichthyotitan in size, potentially making it the largest known marine reptile. It has been estimated at approximately 30 metres in length, which would surpass the blue whale; however, the authors note that this estimate is highly speculative.
The African bush elephant (Loxodonta africana) is the largest living land animal. A native of various open habitats in sub-Saharan Africa, males weigh about on average. The largest elephant ever recorded was shot in Angola in 1974. It was a male measuring from trunk to tail and lying on its side in a projected line from the highest point of the shoulder, to the base of the forefoot, indicating a standing shoulder height of . This male had a computed weight of 10.4 to 12.25 tonnes.
Heaviest living animals
The heaviest living animals are all whales. There are considerable obstacles to overcome in obtaining accurate weights for them, however, as no scale can accommodate the whole body of a large whale. Whaling factories are usually enlisted to help accomplish the task, but it still remains difficult, and most weighings have been done by parts of flensed whales, leaving much room for error. Mathematical formulas have also been devised to estimate the average weight of various whale species based on body length, but this method is equally prone to inaccuracy.
Rank Animal Average massin tonnes Maximum massin tonnes Average total lengthin m (ft) 1 Blue whale 110Mark Tandy. Lives of Whales . Iwcoffice.org 190 24 (79)Blue Whale. The Marine Mammal Center 2 North Pacific right whale 60North Pacific Right Whale Marine education Alaska Sea Grant. Seagrant.uaf.edu (15 February 2008) 120 15.5 (51) 3 Southern right whale 58 110Stewart, et al, National Audubon Society Guide to Marine Mammals of the World. Knofp (2002), 15.25 (50) 4 Fin whale 57 120 21 (69) 5 Bowhead whale 54.5Bowhead Whales, Balaena mysticetus. Marinebio.org (30 September 2011) 120 15 (49) 6 North Atlantic right whale 54Maine Department of Inland Fisheries and Wildlife – Maine Endangered Species Program/Northern Right Whale . Maine.gov 110North Atlantic Right Whale. Animal Info (2 November 2005) 15 (49) 7 Sperm whale 31.25Whitehead, H. (2002). "Sperm whale Physeter macrocephalus". In Perrin, W., Würsig B. and Thewissen, J. Encyclopedia of Marine Mammals. Academic Press. pp. 1165–1172. 80 13.25 (43.5) 8 Humpback whale 29Humpback Whale. Animal Info (1 February 2005) 48 13.5 (44) 9 Sei whale 22.5 45 14.8 (49) 10 Gray whale 19.5 45 13.5 (44)
Heaviest terrestrial animals
The heaviest land animals are all mammals. The African elephant is now listed as two species, the African bush elephant and the African forest elephant, as they are now generally considered to be.African Elephant Really Two Wildly Different Species. News.nationalgeographic.com (22 December 2010)
Rank Animal Average massin tonnes Maximum massin tonnes Average total lengthin m (ft) 1 African bush elephant 6ADW: Loxodonta africana: Information. Animaldiversity.ummz.umich.eduGeorges Frei. Weight and Size of elephants in zoo and circus. Upali.ch 10.4 7.5 (24.6)African Elephant. The Animal Files 2 Asian elephant 4Shoshani, J. and Eisenberg, J. F. Elephas maximus. Mammalian Species (1982) 182:1–8 7 6.5 (21.3) 3 African forest elephant 2.7Forest elephant videos, photos and facts – Loxodonta cyclotis . ARKive 6 6.2 (20.3)Forest Elephant Loxodonta cyclotis – Appearance/Morphology: Measurement and Weight (Literature Reports). Wildpro.twycrosszoo.org 4 White rhinoceros 2White rhinoceros videos, photos and facts – Ceratotherium simum . ARKive (6 August 2004) 4.5 4.4 (14.4)White Rhinoceroses, White Rhinoceros Pictures, White Rhinoceros Facts. Animals.nationalgeographic.com 5 Indian rhinoceros 1.9Indian rhinoceros videos, photos and facts – Rhinoceros unicornis . ARKiveLaurie, W. A.; Lang, E. M. and Groves, C. P. Rhinocerus unicorns . Mammalian Species (1983) 211:1–6 4Boitani, Luigi, Simon & Schuster's Guide to Mammals. Simon & Schuster/Touchstone Books (1984), 4.2 (13.8)Indian rhinoceros . Ultimateungulate.com 6 Hippopotamus 1.8Eltringham, S.K. (1999). The Hippos. Poyser Natural History Series. London: Academic Press. .Hippopotamus. Learnanimals.com 4.5 5.05 (16.5)Hippopotamuses, Hippopotamus Pictures, Hippopotamus Facts. Animals.nationalgeographic.com 7 Javan rhinoceros 1.75Javan Rhinoceros. Animal Info (26 November 2005)Javan Rhino. Onehornedrhino.org 2.3Javan rhinoceros videos, photos and facts – Rhinoceros sondaicus . ARKive 3.8 (12.5)EDGE :: Mammal Species Information Edgeofexistence.org (12 November 2010) 8 Black rhinoceros 1.1Black Rhinoceroses, Black Rhinoceros Pictures, Black Rhinoceros Facts. Animals.nationalgeographic.com 2.9 4 (13.1)ADW: Diceros bicornis: Information. (9 April 2009) 9 Giraffe 1 2Owen-Smith, R. Norman, Megaherbivores: The Influence of Very Large Body Size on Ecology. Cambridge University Press (1992), 5.15 (16.9)Giraffe. The Animal Files 10 Gaur 0.95Smith, A. T., Xie, Y. (eds.) (2008) A Guide to the Mammals of China. Princeton University Press, Princeton Oxfordshire. p. 472 1.5 3.8 (12.5)Walrus: Physical Characteristics . Seaworld.org
Vertebrates
Mammals (Mammalia)
The blue whale is the largest animal, and therefore the largest mammal, of all time, with the longest known specimen being long and the heaviest weighted specimen being 190 tonnes. The extinct whale species Perucetus colossus was shorter than the blue whale, at but it is estimated to have rivaled or surpassed it in weight, at 85–340 tonnes. At the highest estimates, this would make Perucetus the heaviest known animal in history, although more recent estimates put it at a more moderate 60 to 113 tonnesor 35 to 40 tonnes
The largest land mammal extant today is the African bush elephant. The largest extinct land mammal known was long considered to be Paraceratherium orgosensis, a rhinoceros relative thought to have stood up to tall, measured over long and may have weighed about 17 tonnes. In 2015, a study suggested that the extinct elephant Palaeoloxodon namadicus may have been the largest land mammal ever, based on a fragmentary femur estimated to belong to an individual with maximum weight of 22 tonnes. This author also suggested that the extinct mastodon "Mammut" borsoni may have rivalled P. namadicus in size.. However, these estimates remain debated due to the fragmentary nature of the fossil material and the uncertainties involved in scaling from limited remains. In 2022, a study proposed that Dzungariotherium may be the largest paracerathere, surpassing even Paraceratherium thus it represents another contender for the largest terrestrial mammal ever, with estimates of approximately 20.6 tonnes.
Stem-mammals (Synapsida)
The Late Triassic Lisowicia bojani, from what is now southern Poland, probably was the largest of all non-mammalian synapsids (most of which became extinct 250 million years ago), at in length, in height and in weight. However, one study suggested a more conservative weight of 4.87 tonnes to 7.02 tonnes for the adult taxon, with an average body mass of 5.88 tonnes. The largest carnivorous synapsid was Anteosaurus at and .Anteosaurus. Palaeos.com
Caseasaurs (Caseasauria)
The herbivorous Alierasaurus was the largest caseid and the largest amniote to have lived at the time, with an estimated length around . Another huge caseasaur is Cotylorhynchus hancocki, with an estimated length and weight of at least and more than .
Sphenacodontids (Sphenacodontidae)
The biggest carnivorous synapsid of Early Permian was Dimetrodon, which could reach and . The largest members of the genus Dimetrodon were also the world's first fully terrestrial apex predators.
Tappenosaurids (Tappenosauridae)
The Middle Permian Tappenosaurus was estimated at in length which is comparable in size with the largest dinocephalians.
Therapsids (Therapsida)
The plant-eating dicynodont Lisowicia bojani is the largest-known of all non-mammalian synapsids, at and . The largest carnivorous therapsid was the aforementioned Anteosaurus from what is now South Africa during Middle Permian epoch. It reached long, and about in weight.
Reptiles (Reptilia)
The largest living reptile, a representative of the order Crocodilia, is the saltwater crocodile (Crocodylus porosus) of Southern Asia and Australia, with adult males being typically long. The largest confirmed saltwater crocodile on record was long, and weighed about . Unconfirmed reports of much larger crocodiles exist, but examinations of incomplete remains have never suggested a length greater than .Crocodilian Biology Database – FAQ – Which is the largest species of crocodile? Flmnh.ufl.edu Also, a living specimen estimated at and has been accepted by the Guinness Book of World Records.Boloji.com – A Study in Diversity . News.boloji.com However, due to the difficulty of trapping and measuring a very large living crocodile, the accuracy of these dimensions has yet to be verified. A specimen named Lolong caught alive in the Philippines in 2011 (died February 2013) was found to have measured in length.
The Komodo dragon (Varanus komodoensis), also known as the "Komodo monitor", is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang, Nusa kode and Padar. A member of the monitor lizard family (Varanidae), it is the largest living species of lizard, growing to a maximum length of more than in rare cases and weighing up to approximately .