The largest dinosaur in the world is considered to be Brachiosaurus or arm lizard. It was 23 meters in length and 12 meters in height. This was the most complete remains of any big dinosaur found on earth. There were even larger specie of dinosaur found, however, their skeletal remains were too incomplete to determine their exact size. One of them was Argentinasaurus which is said to be twice the size of Brachiosaurus.

 The largest dinosaur is the brontosaurus because it had a long neck.