The Alligator Gar is a large predatory fish introduced to Sri Lanka and is not a native species. Originally found in freshwater and brackish habitats of North America, especially the southern United States and Mexico, it has no natural place in Sri Lanka’s freshwater ecosystems. In Sri Lanka, this species has been reported from some lakes and reservoirs, likely due to illegal release or escape from private ownership. The Alligator Gar is one of the largest freshwater predatory fishes in the world, capable of growing to several metres in length. It has a long, crocodile-like snout filled with sharp teeth and a heavily armored body covered with hard scales. It is an ambush predator that remains motionless before quickly attacking prey. Its diet consists mainly of fish, crustaceans, and other aquatic animals. Due to its large size, powerful predatory behaviour, and ability to consume a wide range of prey, the Alligator Gar is considered a potential threat to Sri Lanka’s native freshwater fish biodiversity. If established in natural lakes and reservoirs, it may compete with native predators and reduce populations of smaller native fishes through predation. As an alien invasive species, the presence of Alligator Gar in Sri Lankan waters is a serious conservation concern. Preventing further releases and monitoring existing populations are important to protect Sri Lanka’s unique freshwater ecosystems and endemic fish species.