A phylogenetic analysis of mitochondrial DNA showed that specimens from Surattani and Nakhon Si Thammarat Provinces in southern Thailand form a deeply divergent clade from those from northern Thailand, which grouped with specimens from Myanmar and Guangdong in southern China. The king cobra's skin is olive green with black and white bands on the trunk that converge to the head. The head is covered by 15 drab coloured and black edged shields. The muzzle is rounded, and the tongue black. It has two fangs and 3–5 maxillar teeth in the upper jaw, and two rows of teeth in the lower jaw. The nostrils are between two shields. The large eyes have a golden iris and round pupils. Its hood is oval shaped and covered with olive green smooth scales and two black spots between the two lowest scales. Its cylindrical tail is yellowish green above and marked with black. It has a pair of large occipital scales on top of the head, 17 to 19 rows of smooth oblique scales on the neck, and 15 rows on the body. Juveniles are black with chevron shaped white, yellow or buff bars that point towards the head. Adult king cobras are long. The longest known individual measured . Ventral scales are uniformly oval shaped. Dorsal scales are placed in an oblique arrangement. The king cobra is sexually dimorphic, with males being larger and paler in particular during the breeding season. Males captured in Kerala measured up to and weighed up to . Females captured had a maximum length of and a weight of . The largest known king cobra was long and captured in Thailand. It differs from other cobra species by size and hood. It is larger, has a narrower and longer stripe on the neck. The head of a mature snake can be quite massive and bulky in appearance. Like all snakes, it can expand its jaws to swallow large prey items. It has proteroglyph dentition, meaning it has two short, fixed fangs in the front of the mouth, which channel venom into the prey. These are behind the usual "nine-plate" arrangement typical of colubrids and elapids, and are unique to the king cobra. The king cobra typically weighs about . A captive one at the London Zoo grew to before being euthanised upon the outbreak of World War II. The heaviest wild specimen was caught at Royal Island Club in Singapore in 1951, which weighed and measured .