The biggest animal ever recorded is the Blue Whale. The longest on record is 33.3 m (109 ft). The heaviest whale on record weighed in at 190 metric tons (210 short tons).
Some of the largest animals that ever lived were the sauropod dinosaurs. There are those who believe that some dinosaur species were larger than the Blue Whale. However, it is difficult to determine because of incomplete fossil remains.
The heaviest and tallest is the sauropod Giraffatitan. The remains were uncovered in Tanzania around 1907. The current estimates say it is 12 m (38 ft) high. The weight has been estimated to be around 30,000 to 60,000 kg (30 to 65 short tons).
The longest dinosaur (and longest land animal ever) is a 25 m (82 ft) long Diplodocus. Many scientists believe that bigger sauropods exist. These would include the Argentinosaurus. Fragmentary remains suggest it weighed 80,000 to 100,000 kg (90 to 110 short tons).
There is also the Supersaurus, which may have reached lengths of 35 m (112 ft). The Sauroposeidon have been as tall as 18 m (60 ft), making it the tallest animal to have existed.
Diplodocus hallorum could have been 35 m (115 ft) long. The Amphicoelias fragillimus may have weighed 60 m (200 ft) long. The Bruhathkayosaurus may be the biggest animal ever recorded. It could have weighed over 200 tons.
The problem here is that dinosaur remains are incomplete. The sizes mentioned for Amphicoelias, Supersaurus, Bruhathkayosaurus and the other sauropods are based on incomplete evidence. This makes accrete sizing very difficult.
Largest Living Land Mammal
The biggest is the African Bush Elephant (Loxodonta africana). The largest specimen weighed 24,000 lb (11,000 kg). It was 3.96 m (13.0 ft) high and 10 m (33 ft) long. It was recorded in 1956.
The saltwater crocodile (Crocodylus porosus) can reach lengths of up to 4.5 to 5 m (15 to 17 ft). The biggest on record weighs 3,000 lb (1,360 kg). It is 20 ft 8 in (6.30 m) long.
The biggest bird today is the ostrich. It is 2.7 m (9 ft) high and weighs 156 kg (345 lb). The egg of an ostrich can weigh as much as 1.4 kg (3 lb). It is the biggest egg on the planet.
The biggest animal ever recorded, as you can see, is still subject to some dispute. For now the Blue Whale is still the biggest. But that may change over time.