A crane fly is a member of the family of insects in the order Diptera, the true flies. The true crane flies are most often classified entirely within the family Tipulidae sensu stricto. Alternately, they are defined as the superfamily Tipuloidea, which includes the Tipulidae and a few other families.

Numerous other common names have been applied to the crane fly, many of them more or less regional, including mosquito hawk, mosquito eater, gallinipper, and gollywhopper. They are also known as daddy-long-legs, not to be confused with arachnids of the order Opiliones or the family Pholcidae. The larvae of crane flies are known commonly as leatherjackets.

Crane flies are widely distributed in general, though individual species usually have limited ranges. They are most diverse in the tropics, and are also common in northern latitudes and high elevations.

The Tipulidae sensu lato is one of the largest groups of flies, including over 15,000 species and subspecies in 525 genera and subgenera. The family sensu stricto includes over 4000 species in 115 genera. Most crane flies were described by the entomologist Charles Paul Alexander, a fly specialist, in over 1000 research publications.