The Arnhold’s mouse lemur or the Montagne d’Ambre mouse lemur (Microcebus arnholdi), is a species of mouse lemur endemic to Madagascar. Its holotype was first collected on 27 November 2005, and was first described in 2008. According to genetic tests, it is genetically distinct from its closest sister taxa, the Sambirano mouse lemur (Microcebus sambiranensis).