The megalopterans are a small order of semiaquatic insects. The larvae are predators in fresh water, whereas the imagines are terrestrial.

They possess wings, but are poor fliers and rarely move far from the hatching site. Megalopterans are closely related to the neuropterans, but can be distinguished from these by the wing veins, which are very coarse and lack the furcations near the wing margin characteristic of the neuropterans.