Abstract: The ruby ant, Myrmica rubra (Linnaeus, 1758) (formerly Myrmica laevinodis Nylander, 1846), an aggressive Eurasian species with a powerful sting, is now spreading through temperate North America. To document the worldwide distribution of M. rubra and evaluate its potential for further spread, we compiled published and unpublished specimen records from > 2000 sites. We report the earliest known M. rubra records for 71 geographic areas (countries, major islands, Us states, Canadian provinces, and Russian federal districts), including three areas with no previously published records: Prince Edward Island, Washington State, and the Far Eastern Federal District of Russia. All earlier published records of M. rubra from East Asia, including the Far East of Russia, Japan, and China, appear to be misidentifications of Myrmica kotokui Forel, 1911. Myrmica rubra is native to an enormous expanse extending from Ireland and Portugal in westernmost Europe across 8000 km to central Asia and eastern Siberia, and from 39 to 70° N in latitude. Exotic populations of M. rubra were first recorded in eastern North America more than 100 years ago. Myrmica rubra is now documented from five southeastern Canadian provinces (New Brunswick, Nova Scotia, Ontario, Prince Edward Island, and Quebec), six northeastern Us states (Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont), and one northwestern state (Washington) ranging from 41.5 to 47.6° N. Given the vast range of M. rubra in Eurasia, perhaps the most striking aspect about this species in North America is how little it has spread over the past century. Most North American records of M. rubra, however, date from the last ten years, suggesting these North American populations are expanding. There appear to be no geographic barriers that would prevent M. rubra from spreading across the Us and Canada, from coast to coast.