Largest and heaviest animals

The largest animal currently alive 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. 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.
In 2023, paleontologists estimated that the extinct whale Perucetus, discovered in Peru, may have outweighed the blue whale, with a mass of. However, more recent studies suggest this whale was much smaller than previous estimates, putting its weight at 60 to 113 tonnes. 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. 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. 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.
The African bush elephant 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 mass in tonnes	Maximum mass in tonnes	Average total length in m
1	Blue whale	110	190	24
2	North Pacific right whale	60	120	15.5
3	Southern right whale	58	110	15.25
4	Fin whale	57	120	21
5	Bowhead whale	54.5	120	15
6	North Atlantic right whale	54	110	15
7	Sperm whale	31.25	57	13.25
8	Humpback whale	29	48	13.5
9	Sei whale	22.5	45	14.8
10	Gray whale	19.5	45	13.5

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.

Rank	Animal	Average mass in tonnes	Maximum mass in tonnes	Average total length in m
1	African bush elephant	6	10.4	7.5
2	Asian elephant	4.5	7	6.5
3	African forest elephant	2.7	6.0	6.2
4	White rhinoceros	2	4.5	4.4
5	Indian rhinoceros	1.9	4.0	4.2
6	Hippopotamus	1.8	4.5	5.05
7	Javan rhinoceros	1.75	2.3	3.8
8	Black rhinoceros	1.1	2.9	4
9	Giraffe	1.0	2	5.15
10	Gaur	0.95	1.5	3.8

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 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.

Stem-mammals ([Synapsida])

The Late Triassic Lisowicia bojani, from what is now southern Poland, probably was the largest of all non-mammalian synapsids, 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.

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 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. Also, a living specimen estimated at and has been accepted by the Guinness Book of World Records. 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 was found to have measured in length.
The Komodo dragon, 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, it is the largest living species of lizard, growing to a maximum length of more than in rare cases and weighing up to approximately.
Nevertheless, current extant reptiles are still dwarfed by their prehistoric ancestors. The largest non-dinosaurian terrestrial reptile to have ever lived were crocodilomorphs such as Deinosuchus, Sarcosuchus and Purussaurus, each have weight varying between 5–10 metric tons. The largest snake to have ever lived was Titanoboa which could grow up to and weigh up to. Prehistoric marine reptiles from the Mesozoic were even larger. Archelon was the largest testudines, being around long from head to tail and in weight. Mosasaurus hoffmanni was the largest squamate lizard to have ever lived, with a length of and a body mass of However, the largest reptiles were the shastasaurids, specifically Ichthyotitan, which approached lengths rivalling to exceeding those of a blue whale, at around in length.

Largest living reptiles

The following is a list of the largest living reptile species ranked by average weight, which is dominated by the crocodilians. Unlike mammals, birds, or fish, the mass of large reptiles is frequently poorly documented and many are subject to conjecture and estimation.

Rank	Animal	Average mass	Maximum mass	Average total length
1	Saltwater crocodile	450	2,000	4.5
2	Nile crocodile	410	1,090	4.2
3	Orinoco crocodile	380	1,100	4.1
4	Leatherback sea turtle	364	932	2.0
5	American crocodile	336	1,000	4.0
6	Black caiman	300	1,000	3.9
7	Gharial	250	1,000	4.5
8	American alligator	240	1,000	3.4
9	Mugger crocodile	225	700	3.3
10	False gharial	210	590	4.0
11	Aldabra giant tortoise	205	360	1.4
12	Loggerhead sea turtle	200	545	0.95
13	Green sea turtle	190	395	1.12
14	Slender-snouted crocodile	180	325	3.3
15	Galapagos tortoise	175	417	1.5