The King Cobra ( Ophiophagus hannah ) is a species of the Elapidae family . It is the world 's longest venomous snake with a length that can be as large as 5.6 m ( 18.5 ft ) . The king cobra ( Ophiophagus hannah ) is the world 's longest venomous snake , with a length up to 5.6 m ( 18.5 ft ) .