Here are a few contenders, each claiming the title in a different way:
By Weight:
* Blue Whale: This magnificent creature can reach up to 200 tons and over 100 feet long. They are the undisputed heavyweight champion of the animal kingdom.
By Length:
* Blue Whale: Again, the blue whale takes the crown, reaching lengths of over 100 feet.
* Giant Squid: While not as heavy as the blue whale, the giant squid is a strong contender for longest animal. They can reach lengths of 43 feet! However, we know very little about them because they live in the deep ocean.
By Height:
* Giraffe: These tall creatures can reach heights of over 19 feet!
By Area Covered:
* Honeycomb Mushroom: This fungus can spread across an area of over 2,000 acres! However, it's worth noting that this is a single organism, not a single animal.
So, the answer to your question really depends on what criteria you're using to measure "biggest."