Madame Berthe's mouse lemur (Microcebus berthae) or Berthe's mouse lemur is the smallest of the mouse lemurs and the smallest primate in the world; the average body length is and seasonal weight is around . Microcebus berthae is one of many species of Malagasy lemurs that came about through extensive speciation, caused by unknown environmental mechanisms and conditions. This primate is found chiefly in the Kirindy forest in western Madagascar. After its discovery in 1992 in the dry deciduous forest of western Madagascar, it was initially thought to represent a rediscovery of M. myoxinus, but comparative morphometric and genetic studies revealed its status as a new species, M. berthae.