Leishmania is a protist organism which causes Leishmaniasis. It is a Trypanosomatid parasite in the Euglenozoa phylum.

It is spread by sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World.

Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans. Leishmania currently affects 12 million people in 98 countries. The parasite was named in 1903 after the Scottish pathologist William Boog Leishman.