Which snake has the longest fangs of any snake, reaching about 5 centimetres?

The Gaboon viper has the longest fangs of any snake, reaching about 5 centimetres.

The Gaboon viper, Bitis gabonica, is a large African viper found in forest and woodland habitats across parts of sub-Saharan Africa. Its hinged solenoglyphous fangs fold against the roof of the mouth when unused and swing forward during a strike.

The fangs are exceptionally long because the species has a broad head and a large venom-delivery system. Despite its imposing equipment, the Gaboon viper is generally slow-moving and relies heavily on camouflage among leaf litter. Its patterned body resembles fallen leaves and dappled forest floor.

Long fangs do not make it the longest or most venomous snake. Fang length, venom toxicity, venom quantity and defensive behaviour are separate traits, so comparisons depend on the measurement being used.