What is the largest animal on the Earth?

Largest of the planet : blue whale, largest on land : African elephant.

A female blue whale weighing 190 tonnes (over 420,000 lbs.) and measuring 27.6 m (90 ft 6 in) in length was caught on March 20, 1947.
Source: Guinness World Records

Everything about the blue whale is enormous. It is the largest animal on earth, ever. A big blue whale can be 100 feet long and weigh up to 150 tons. That's as large as a Boeing jet. Its heart is as large as a small car. Fifty people could stand on its tongue. Its spout shoots up at least 30 feet when it surfaces for air.

http://school.discoveryeducation.com/schooladventures/planetocean/bluewhale.html

You may have already thought you guessed it’s an elephant, but the biggest animal on our planet is the blue whale. Elephant are the biggest land animals with 13 and half tons which the heaviest one had. Still, the biggest blue whale ever recorded had around 180 tons (180.000 kg!) and was long 30 m (hundred feet).

http://www.biggestintheworld.org/biggest-animal-in-the-world/

[Added text from the reference link. - McG]