<p>Lake Geneva (Léman), the largest lake in Western Europe, is a vital freshwater ecosystem that supports a range of essential services, including water supply, fisheries, navigation, and recreational activities. However, like many other freshwater systems, it faces numerous threats that jeopardize its ecological integrity. These threats not only endanger the lake’s biodiversity but also impact the ecosystem’s overall functioning and the services it provides. One potential significant threat is the occurrence of algal blooms, particularly those involving toxic species such as pelagic cyanobacteria. These blooms can disrupt vital ecological processes and pose serious risks to animal and human health, local fisheries, and the regional economy. This article reviews the history of algal blooms in Lake Geneva over the last 70 years, aiming to identify the species involved and the services impacted, examine the common and unique factors driving these proliferations, and propose potential future scenarios in the context of both local and global changes. The ultimate goal is to inform effective management strategies to mitigate the impacts of these blooms.</p>