Freshwater ecosystems are particularly susceptible to invasions by invasive non-native species (INNS) across a range of taxa, largely as a consequence of anthropogenic influences on these systems, with a number of ecological and socio-economic impacts. This chapter reviews freshwater invasive non-native species across the globe, focusing on fishes, invertebrates, floating macrophytes, and submerged macrophytes emphasising the knowledge gaps in particular that have resulted in biases inherent in assessments of freshwater invasions. These include an ecological bias because the majority of studies focus on terrestrial invasions; a geographical bias as most studies are focused on temperate northern hemisphere systems; and a taxon bias where fish invasions, populate the literature. This chapter highlights some of the approaches needed to survey, monitor, and manage INNS.