The longest dinosaur to exist is Argentinosaurus.

Argentinosaurus, a colossal dinosaur of the Late Cretaceous period, holds the distinction of being one of the largest land animals to have ever walked the Earth. While our understanding of this magnificent creature is based on limited fossil remains, the discoveries made thus far have revealed its incredible size and significance in the realm of prehistoric giants.

Belonging to the group of titanosaurs, Argentinosaurus is estimated to have reached lengths of up to 40 meters (131 feet) and weighed around 70 to 100 tons. Its massive body was supported by sturdy limbs and a robust skeletal structure, allowing it to traverse the ancient landscapes with its immense weight.

Although few fossil fragments of Argentinosaurus have been found, its skeletal remains indicate a herbivorous dinosaur with a relatively small head in proportion to its colossal body. This suggests that Argentinosaurus likely had a long neck, enabling it to reach vegetation high above the ground.