The Argentine ant, Linepithema humile (Mayr, 1868), is a highly invasive species with serious detrimental consequences to native fauna and flora in invaded territories. Native to South-Central South America, it was first reported from continental Africa in 1893 but, to date, had never been recorded from the Malagasy region (encompassing Madagascar, Comoros, Seychelles, and Mascarene archipelago). Here, we report the first record of this invasive species on the island of La Réunion, a French overseas territory part of the Mascarene archipelago. The species was identified using both morphological and molecular analysis. We discuss potential ecological consequences of the presence of this ant on the insular ecosystems of La Réunion.