A Dobsonfly is any insect of the subfamily Corydalinae, part of the megalopteran family Corydalidae. There are over 220 species of dobsonflies. Dobsonflies are found throughout the Americas and Asia, as well as South Africa. Their closest relatives are the fishflies.

Both male and female dobsonflies can reach lengths up to five inches (12.5 cm), measured from the tips of their pincers to the tips of their four wings. Their wingspans can be twice as long as their body length. The wings are densely lined with intersecting veins. When not in use, the wings are folded along the length of their bodies. Dobsonflies have long, multi-segmented antennae.

Though both male and female dobsonflies have sharp mandibles, those of an adult male dobsonfly are actually so big – up to 1 inch (25 mm) – that they are unable to harm humans, as they have such poor leverage that they are incapable of breaking the skin. Their mandibles are used exclusively during mating, where males show them off and grasp the females during copulation. Female dobsonflies, however, retain the short, powerful pincers they had as larvae, so they can inflict painful bites, which can draw blood. Notwithstanding the males' inability to inflict harm, when threatened both sexes will raise their heads and spread their jaws menacingly. They are not venomous, but possess an irritating, foul-smelling anal spray as a last-ditch defense.

Dobsonflies spend most of their life in the larval stage, during which they are called hellgrammites, "go-devils" or "crawlerbottoms", and are familiar to anglers who like to use the large larvae as bait. Hellgrammites live under rocks at the bottoms of lakes, streams and rivers, and prey on other insect larvae with the short sharp pincers on their heads, with which they can also inflict painful bites on humans. The larvae reach to 2" to 3" in length, with gills all along the sides of their segmented bodies that allow them to extract oxygen from water. They are a great catfish bait, as their leather like skin does not allow them to be removed from a hook easily by a fish^{[citation needed]}.