"Freshwater ecosystems of islands in the Caribbean Sea are underappreciated critical habitats for locally endemic biodiversity, and are threatened by the presence of a growing number of nonindigenous species. Xiphophorus maculatus (Southern Platyfish) is a popular ornamental fish species that has been widely introduced outside its native range of eastern Mexico. We surveyed freshwater fishes from urban environments of Guadeloupe and conducted a preliminary molecular phylogenetic analysis to verify species identifica-tion. Sanger sequences generated from PCR amplicons of the cytochrome oxidase I gene were used to verify the presence of 2 invasive freshwater fishes. We report the occurrence of X. maculatus from the French Department of Guadeloupe, which represents the first ob-servation of this species in the Lesser Antilles ecoregion. We also confirmed the presence of Poecilia reticulata (Guppy) using genetic sequence data. We characterize the risk posed by invasive poeciliids by listing the native fauna that may be negatively impacted through competition, predation, or by exposure to parasites and pathogens, and conclude by high-lighting the need for coordinated invasive species management plans involving multiple stakeholders of the Caribbean ecoregion." . "Alley et al. (2023)" . . "2023"^^ . . "2023"^^ . . "Freshwater ecosystems of islands in the Caribbean Sea are underappreciated critical habitats for locally endemic biodiversity, and are threatened by the presence of a growing number of nonindigenous species. Xiphophorus maculatus (Southern Platyfish) is a popular ornamental fish species that has been widely introduced outside its native range of eastern Mexico. We surveyed freshwater fishes from urban environments of Guadeloupe and conducted a preliminary molecular phylogenetic analysis to verify species identifica-tion. Sanger sequences generated from PCR amplicons of the cytochrome oxidase I gene were used to verify the presence of 2 invasive freshwater fishes. We report the occurrence of X. maculatus from the French Department of Guadeloupe, which represents the first ob-servation of this species in the Lesser Antilles ecoregion. We also confirmed the presence of Poecilia reticulata (Guppy) using genetic sequence data. We characterize the risk posed by invasive poeciliids by listing the native fauna that may be negatively impacted through competition, predation, or by exposure to parasites and pathogens, and conclude by high-lighting the need for coordinated invasive species management plans involving multiple stakeholders of the Caribbean ecoregion." . "Alley, Z., Fast, K., Delolme, J. & Sandel, M. 2023. First Report of Xiphophorus maculatus (Gunther) (Southern Platyfish) and Confirmation of Poecilia reticulata (Peters) (Guppy) from Guadeloupe-France. Caribbean Naturalist, 90: 1-12." . "Alley et al. (2023)" .