Warble fly is a name given to the genus Hypoderma: large flies which are parasitic on cattle and deer. Other names include "heel flies", "bomb flies" and "gadflies", while their larvae are often called "cattle grubs" or "wolves." Common species of warble fly include Hypoderma bovis (the ox warble fly) and Hypoderma lineatum (the cattle warble fly) and Hypoderma tarandi (the reindeer warble fly). Larvae of Hypoderma species also have been reported in horses, sheep, goats and humans. They have also been found on smaller mammals such as dogs, cats, squirrels, voles and rabbits.

Adult warble flies are large, hairy and bumblebee-like and brown, orange or yellow in color. The adults have vestigial mouthparts, so they cannot feed during their short lifespans, which can be as little as five days.

They are found on all continents of the Northern Hemisphere, mainly between 25° and 60° latitude.