Philornis is a genus of around 50 species of fly (Diptera, Muscidae) from Central and South America. Their larvae are subcutaneous parasites of nestling birds. They parasitize a wide range of bird species including macaws at the Tambopata research site.
Two species are also found in the southern United States. One species, Philornis downsi has been accidentally introduced to the Galapagos Archipelago posing a major threat to some of its endemic birds.