There are around 28 to 30 species of snakes commonly referred to as cobras. If any snake that has a hood and can raise its upper body is considered to be a cobra, then there may be as many as 270 species of cobra.
The word "cobra" is commonly used to refer to any of a number of venomous snakes found in Africa and Southeast Asia. True cobras are members of the genus Naja, which includes the common Indian cobra. The largest of the cobras, the king cobra, is not a member of the genus Naja but is instead in its own genus, Ophiophagus. The spitting cobra is also not considered to be part of the genus Naja; it also has its own genus, Hemachatus.