The largest animal to have ever lived is the blue whale (Balaenoptera musculus). These magnificent marine mammals can reach lengths of up to 100 feet (30 meters) and can weigh as much as 200 tons or more. The blue whale's heart alone can weigh as much as a small car, highlighting their immense size. They inhabit oceans around the world, including both temperate and polar waters. Fortunately, conservation efforts have been put in place to protect blue whales, which were heavily hunted in the past. Today, their populations are gradually recovering, making them an inspiring success story in marine conservation.