Technical Abstract: Deciphering the geographic origins of pathogens and elucidating the population biology of these microscopic organisms are necessary steps to establish effective disease-control strategies. The generalist ascomycete fungus Eutypa lata causes Eutypa dieback of grapevine (Vitis vinifera) worldwide. To identify centers of diversity and new introduction areas for E. lata, and to reveal migration patterns among continents, we investigated the population genetic structure of 20 geographic populations from four continents, based on analyses of 294 isolates genotyped with nine microsatellite markers. The greatest levels of genetic diversity were found in Europe, where two genetically-divergent clusters were identified. One cluster included isolates mainly from inland areas. The other cluster, genetically more diverse, included isolates mainly from coastal areas surrounding the Mediterranean Sea. Populations in California, Australia and South Africa, all of which had significantly lower genetic diversity than in Europe, were also characterized by demographic disequilibrium, and thus may represent founding populations of the pathogen. Low levels of genetic differentiation between the inland European cluster and the three putative founding populations suggest that they have a European origin, with a relatively short period of time since introduction. The patterns of genetic diversity among the populations are consistent with the historic, worldwide movement of the pathogen’s host, V. vinifera, and the history of its cultivation.