Synanceia is a genus of fish of the family Synanceiidae, the Stonefishes, whose members are venomous, dangerous, and even fatal to humans. It is the most venomous fish in the world. They are found in the coastal regions of Indo-Pacific oceans.
Synanceia are primarily marine, though some species are known to live in rivers. Its species have potent neurotoxins secreted from glands at the base of their needle-like dorsal fin spines which stick up when disturbed or threatened. The vernacular name of the species, the stonefish, derives from being able to camouflage and transform itself to a grey and mottled color similar to the color of a stone. Divers have sometimes stepped on them, thinking they are stones. When these fish get stepped on, the pressure of how hard it is stepped on releases a certain amount of venom.