Located at the crossroad of the Palearctic, Saharo-Arabian, and Oriental zoogeographic realms, and with its great environmental diversity, Iran harbors a high complexity and richness of fauna and flora. Knowledge about the Iranian mammal fauna has greatly increased over recent years thanks to the growing availability of molecular tools, which brought marked changes in taxonomy, but also because of intensive field surveys resulting in growing distributional data. These data are, however, scattered throughout numerous publications and unpublished sources, most of which are difficult to access. Here, we present a comprehensive review of the current mammal species taxonomies with an update on systematics and their spatial distribution based on all possible sources spanning the period between 1758 and today. We updated the geographical distribution of all Iranian land mammals, providing their regional extent of occurrence and area of occupancy, as well as mapped species richness. Based on this information, we then assessed the conservation status of Iran's mammals using the International Union for Conservation of Nature Red List criteria, providing a regional status assessment. The current species list of terrestrial mammals of Iran comprises 192 species from 34 families, of which eight species are endemics. Since the publication of Karami et al. (2008), 13 new species or new records have been added to the mammals of Iran and 32 changes in classification or nomenclature have been made. The Alborz and Zagros mountains accumulate the highest species richness. Nearly 13% of the species in Iran are threatened, and a further 14% are near to qualifying for threatened status. With the current review, we provide an up-to-date summary of the current knowledge about the terrestrial mammals of Iran that can serve as a guideline for mammalogists, a reference for monitoring regional biodiversity status and trends, and a framework for planning management actions to sustain biodiversity conservation.