The Korean Peninsula and its associated Pacific islands have a distinctive, yet poorly studied mammalian fauna. Korea was a land of invasions and wars for many centuries. The loss of large mammals per unit area that has occurred in Korea may have been greater than in any other country. The peninsula has a depauperate rodent community. The forests are mostly harvested, replaced by intensive agriculture. Unfortunately, the dissemination of information about the mammals of Korea and their taxonomy has been limited because most publications were written in Japanese or Korean. We provide an updated checklist of all the species of Korean mammals, including a review of their taxonomy, distribution, and conservation status based on information extracted from international museum collections, local survey databases (Wildlife Survey and National Nature-Environmental Survey, South Korea) and a literature review. We identify 84 species of terrestrial mammals and 43 species of marine mammals that occur, or once occurred, in Korea. Due to previous, erroneous identifications, we delisted three soricids, two vespertilionids, one phocid, one sciurid and one murid. In total, we confirm the presence in Korea of 127 species of mammals distributed in eight Orders and 32 Families. We provide dichotomous keys for the identification of all the Korean species of mammals together with updated distribution maps.