Hellbenders are not the largest salamanders in the world, but they're pretty close. Their close relatives, salamanders in the genus Andrias , can reach lengths over 5 feet. Hellbenders have a flat body and head, a large, very keeled tail, and tiny eyes. Many individuals have fleshy folds of skin along the sides of their body which help to take in oxygen from the water. The arms and legs are very large and muscular and each hand and foot has 5 fingers.
Hellbenders can range in color from dull brown or gray to bright orange or red.
They usually have some sort of darker spots or blotches on their bodies, but the belly is usually only one color. This makes them very difficult to catch and to handle, but the slime is not poisonous. It quickly dropped the salamander with distaste. Hellbenders do have many, tiny teeth, but they usually don't try to bite. Unlike mudpuppies, hellbenders have external gills only as larvae.