Leishmania is a parasitic protozoan, a single-celled organism of the genus Leishmania that is responsible for the disease leishmaniasis. They are spread by sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. At least 93 sandfly species are proven or probable vectors worldwide. Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans.

The Phlebotominae are a subfamily of the family Psychodidae. In several countries, their common name is sandfly, but that name is also applied to other flies. The Phlebotominae include many genera of blood-feeding (hematophagous) flies, including the primary vectors of leishmaniasis, bartonellosis and pappataci fever. In the New World, leishmaniasis is spread by sand flies in the genus Lutzomyia, which commonly live in caves, where their main hosts are bats. In the Old World, sand flies in the genus Phlebotomus spread leishmaniasis.