Dragonflies and damselflies together make up their own order of insects known as Odonata. Dragonflies are large insects and make up the suborder Anisoptera, damselflies are smaller and make up the suborder Zygoptera. Dragonfly, is the common name for any member of an order of predaceous aquatic insects with an elongated body, agile flight, and two pairs of membranous wings. The order is divided into two suborders: the dragonflies and the damselflies. About 5900 species are known; members are found in all temperate and tropical regions of the world.

Dragonflies existed before dinosaurs. A fossilised impression of a dragonfly wing, found in a coal mine in England, is the oldest known dragonfly specimen, it lived 300 million years ago and had a wingspan of eight inches. The largest known dragonfly had a wingspan of 24 inches. Today, the largest dragonfly is found in South America with a wingspan of over seven inches. Other than being smaller, modern-day dragonflies do not look very different from their ancestors.

Dragonflies have a large head, which consists largely of compound eyes, each eye being made up of thousands of six-sided units, providing excellent eyesight and enabling a dragonfly to detect even the slightest movement. Their short antennae are hairlike. Their mouth parts are adapted for biting and scooping prey from the air, as a predatory insect, they hover over a pond before darting at their prey. The immature forms live in freshwater as predators, feeding on other invertebrates, while adult Dragonflies are always on the hunt, they use their fierce jaws to catch large quantities of small flying insects. Dragonflies are sometimes called "mosquito hawk" because they catch and eat so many mosquitoes. Dragonflies' ability to manoeuvre makes them able to out-fly their prey.

Dragonflies have a strong thorax, a long slender body with an elongated abdomen. Dragonflies and damselflies play an important part in the food chain of freshwater streams and lakes.

Their two pairs of narrow, net-veined wings that are usually held outstretched at right angles to the body while the insect is at rest. The front pair of wings are slightly longer than the back pair. Most temperate zone species of dragonflies have wingspans of 5 to 8 centimetres or 2 to 3 inches, but wingspans of tropical species may reach 20 centimetres or 8 inches.

During flight, small, powerful "tornadoes" of air move along the front wings. These tiny tornadoes help the dragonfly maintain its lift, while the back wings stop the "tornadoes" from breaking up. Their legs are located far forward on the body and are used mainly to grasp resting spots such as twigs.

Male dragonflies exhibit territorial behaviour and will stake out an area continuously patrolling while awaiting a passing female. He will chase other males from the area.

The dragonfly begins its life as an egg. Adult female dragonflies lay their eggs on or in water or on water plants and the larvae are aquatic. The eggs hatch after about two weeks and an immature dragonfly, or nymph, emerges. The nymphs are not pretty like the adults, having tiny wings and a large lower lip, used to catch their prey, often mosquito larvae. Dragonfly nymphs live in the water. As they grow, they moult. Nymphs of some species may take as long as three years to mature.

When a dragonfly nymph reaches maturity, it crawls out of the water onto a plant stem. Its skin begins to split, first the head, then the thorax, then the legs, finally the wings of an adult dragonfly emerge. After a couple of hours it is able to fly. It takes about two days before the adult dragonfly's beautiful colours are fully developed. Adult dragonflies live only a few months.

The fastest insect is the Australian dragonfly, verified at 55 miles per hour.