Nealcos is an aquatic-type Zoanoid that appears in the Guyver manga and anime. It is the most common of Cronos' aquatic-based Zoanoids, first field-tested on land during the Takeshiro Incident and put to effective use on land and in water during the X-Day conflict.

Although rather slender as Zoanoids go, Nealcos is the strongest of the aquatic-types and can operate at over a thousand feet underwater, making it highly effective for attacking and boarding submarines.