legendary monster usually conceived as a huge, bat-winged, fire-breathing, scaly lizard or snake with a barbed tail. The belief in these creatures apparently arose without the slightest knowledge on the part of the ancients of the gigantic, prehistoric, dragon-like reptiles. In Greece the word drakōn, from which the English word was derived, was used originally for any large serpent (see sea serpent), and the dragon of mythology, whatever shape it later assumed, remained essentially a snake.

In general, in the Middle Eastern world, where snakes are large and deadly, the serpent or dragon was symbolic of the principle of evil. Thus, the Egyptian god Apepi (Apopis), for example, was the great serpent of the world of darkness. But the Greeks and Romans, though accepting the Middle Eastern idea of the serpent as an evil power, also at times conceived the drakontes as beneficent powers—sharp-eyed dwellers in the inner parts of the Earth. On the whole, however, the evil reputation of dragons was the stronger, and in Europe it outlived the other. Christianity confused the ancient benevolent and malevolent serpent deities in a common condemnation. In Christian art the dragon came to be symbolic of sin and paganism and, as such, was depicted prostrate beneath the heels of saints and martyrs.

The dragon's form varied from the earliest times. The Chaldean dragon Tiamat had four legs, a scaly body, and wings, whereas the biblical dragon of Revelation, “the old serpent,” was many-headed like the Greek Hydra. Because they not only possessed both protective and terror-inspiring qualities but also had decorative effigies, dragons were early used as warlike emblems. Thus, in the Iliad, King Agamemnon had on his shield a blue three-headed snake, just as the Norse warriors in later times painted dragons on their shields and carved dragons' heads on the prows of their ships. In England before the Norman Conquest, the dragon was chief among the royal ensigns in war, having been instituted as such by Uther Pendragon, father of King Arthur. In the 20th century the dragon was officially incorporated in the armorial bearings of the prince of Wales.

In the Far East, the dragon managed to retain its prestige and is known as a beneficent creature. The Chinese dragon, lung (q.v.), represented yang, the principle of heaven, activity, and maleness in the yin-yang (yinyang) (q.v.) of Chinese cosmology. From ancient times, it was the emblem of the Imperial family, and until the founding of the republic (1911) the dragon adorned the Chinese flag. The dragon came to Japan with much of the rest of Chinese culture, and there (as ryū or tatsu) it became capable of changing its size at will, even to the point of becoming invisible. Both Chinese and Japanese dragons, though regarded as powers of the air, are usually wingless. They are among the deified forces of nature in Taoism.

The term dragon has no zoological meaning, but it has been applied in the Latin generic name Draco to a number of species of small lizards found in the Indo-Malayan region. The name is also popularly applied to the giant monitor, Varanus komodoensis, discovered on Komodo, in Indonesia.