List of largest fish

Fish vary greatly in size. The extant whale shark and basking shark exceed all other fish by a considerable margin in weight and length. With the extinct Otodus megalodon exceeding all other fish extant and extinct (excluding tetropods) in size. Fish are a paraphyletic group that describes aquatic vertebrates while excluding tetrapods, and the bony fish that often represent the group are more closely related to tetropods such as whales, than to the cartilaginous fish such as sharks and rays. As such, cross group comparisons on this page only serve a colloquial purpose.
The largest fish of the now-extinct class Placodermi was the giant predatory Dunkleosteus. The largest and most well known species was D. terrelli, which grew almost 4.1 m (13.5 ft) in length Engelman (2023), using an ellipsoid volumetric method, estimated weights of 950–1,200 kilograms (2,090–2,650 lb) for typical (3.41 metres (11.2 ft) long) adult Dunkleosteus, and weights of 1,494–1,764 kilograms (3,294–3,889 lb) for the largest (4.1 metres (13.5 ft)) individual. Its filter feeding relative, Titanichthys, may have rivaled it in size. Titanichthys reached a length of 7 m (23 ft) though in older paper it was estimated at 7.5 m (25 ft). However, according to a 2023 paper, it would have been the same size as Dukleosteus.
The cartilaginous fish are not directly related to the "bony fish," but are sometimes lumped together for simplicity in description. The largest living cartilaginous fish, of the order Orectolobiformes, is the whale shark (Rhincodon typus), of the world's tropical oceans. It is also the largest living animal that is not a cetacean and, like the largest whales, it is a docile creature that filter-feeds on tiny plankton. An average adult of this species measures 9.7 m (32 ft) long and weighs an average of 9 tonnes. The largest verified specimen was caught in 1949 off Karachi, Pakistan and was 12.7 m (42 ft) long and weighed 21.5 tonnes (21.2 long tons; 23.7 short tons). Although many are dubious, there are several reports of larger whale sharks, with reliable sources citing unverified specimens of up to 37 tonnes (36 long tons; 41 short tons) and 17 m (56 ft) or possibly up to 21.9 metres (72 ft).
The extinct Megalodon is estimated to have been the largest Cartilagenous fish as well as largest non-tetrapod fish. It was macropredatory feeding mainly on marine mammals. With maximum total length estimates ranging from 14.3–24.3 metres (47–80 ft).
The largest of the now-extinct Acanthodii was Xylacanthus grandis, an ischnacanthiform based on a ~35 cm (14 in) long jaw bone. Based on the proportions of its relative Ischnacanthus, X. grandis had an estimated total length of 2.5 m (8 ft 2 in).
The largest living bony fish (superclass Osteichthyes, which includes both ray-finned and lobe-finned fish) are the lesser known southern sunfish (Mola alexandrini) followed by widely distributed and better known ocean sunfish (Mola mola) and, both being members of the order Tetraodontiformes. The largest verified specimen belongs to the southern sunfish discovered dead near the Azores in the Atlantic has set the record for being the largest extant bony fish with the weight of 2,744 kg (6,049 lb). The record size ocean sunfish crashed into a boat off Bird Island, Australia in 1910 and measured 4.3 m (14 ft) from fin-to-fin, 3.1 m (10 ft) in length and weighed about 2,300 kg (5,100 lb), while the other record for the biggest bony fish is yet held by a Mola alexandrini which was also coincidentally 2,300 kg (5,100 lb) in mass and 3 m (9.8 ft) in length, caught off in 1996 and misidentified as a Mola mola.
As for length, the longest extant bony fish on earth is the giant oarfish (Regalecus glesne). Slender and compressed, it averages over 6 m (20 ft) long at maturity. A specimen caught in 1885 of 7.6 m (25 ft) in length weighed 275 kg (606 lb). The longest known example, which was hit by a steamship, was measured as 13.7 m (45 ft) long.
Much larger bony fish existed prehistorically, the largest ever known having been Leedsichthys of the Jurassic period. This species is certainly the largest bony fish ever and one of the largest non-cetacean marine animals to have ever existed. Estimates of the size of this fish range from 21 to 27 m (69 to 89 ft) and mass from 20 to 50 tons. A maximum size of 22 m (72 ft) and 25–30 tons had been deemed to be most realistic. However, a 2013 study which estimated the maximum size of the animal based on the largest specimens it is estimated that Leedsichthys would have a maximum length of 16.5 metres (54 ft) and a maximum weight of 49 tonnes (108,000 lb).
The largest living (non-tetrapod) lobe-finned fish is the coelacanth. The average weight of the living West Indian Ocean coelacanth, (Latimeria chalumnae), is 80 kg (180 lb), and they can reach up to 2 m (6.6 ft) in length. Specimens can weigh up to 110 kg (240 lb). The largest lobe-finned fish of all time was Rhizodus at up to 7 m (23 ft).