The largest animal that ever lived, is alive now, and is the Blue Whale, however, there are two Dinosaurs that could perhaps be larger. Amphicoelias Fragillimus, which if existed would have been up to 196 feet long and 122 tons. Also, Bruhathkayosaurus Matleyi, which possibly was 110 feet long and 139 tons. Blue Whales reach 108 feet long and 172 tons. The Blue Whale is the heaviest animal ever, but possibly not the longest.