The biggest animal in the world is the blue whale (Balaenoptera musculus), which is also the largest mammal on Earth. Adult blue whales can grow up to 100 feet long (around 30 meters) and weigh more than 200 tons. They feed on krill, a tiny shrimp-like crustacean, and can consume up to 4 tons of krill per day. Despite being enormous in size, these gentle giants are filter feeders and do not pose any threat to humans.