The Komodo dragon (Varanus komodoensis), also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang, and Padar. A member of the monitor lizard family (Varanidae), it is the largest living species of lizard, growing to a maximum length of 3 metres (10 ft) in rare cases and weighing up to around 70 kilograms (150 lb). Their unusual size has been attributed to island gigantism, since no other carnivorous animals fill the niche on the islands where they live.

However, recent research suggests the large size of Komodo dragons may be better understood as representative of a relict population of very large varanid lizards that once lived across Indonesia and Australia, most of which, along with other megafauna, died out after the Pleistocene. Fossils very similar to V. komodoensis have been found in Australia dating to greater than 3.8 million years ago, and its body size remained stable on Flores, one of the handful of Indonesian islands where it is currently found, over the last 900,000 years, "a time marked by major faunal turnovers, extinction of the island's megafauna, and the arrival of early hominids by 880 ka."

As a result of their size, these lizards dominate the ecosystems in which they live. Komodo dragons hunt and ambush prey including invertebrates, birds, and mammals. Their group behaviour in hunting is exceptional in the reptile world. The diet of big Komodo dragons mainly consists of deer, though they also eat considerable amounts of carrion. Komodo dragons also occasionally attack humans in the area of West Manggarai Regency where they live in Indonesia.