Four species of the temperate ant genus Myrmica are found on Taiwan, all except M. serica are known only from the island. Three are previously described species (M. formosae, M. Serica and M. arisana) and the fourth is an hitherto unknown species (M. mirabile). The status of all four species is reviewed and a key to their identification is provided. M. mirabile has exceptionally large workers for a Myrmica ant, and differs in this respect from all other known species except M. gigantea (Collingwood).