What is the largest animal ever?

Answer 1

The blue whale is generally believed to be the largest animal that ever lived. But there has been a jellyfish that was bigger than the blue whale. It was a lion's mane jellyfish found on the shore of Massachusetts Bay in 1861.
The Blue Whale is believed to be the largest species ever to exist on Earth.

Answer 2

Deinocheirus, a large ornithomimosaur from the Late Cretaceous, was about 11m long and weighed 14,000 lb

Answer 3

The giant anteater.