Myiasis is the invasion of human or animal tissues by fly larvae which may cause significant morbidity and rarely mortality. The condition may be accidental (accidentally ingesting fly eggs or larvae), facultative (flies opportunistically laying eggs in wounds on animals and humans), or obligate (fly larvae that must spend part of their life cycle in living tissue). This chapter explores the various types of myiasis, the fly species involved, and contributing factors. Myiasis prevention, control, diagnosis, and treatment strategies are also presented and discussed.