A cave dweller or caveman was a being inhabiting a cave, and was often associated with primitive cultures.
On ancient Earth, Troglodyte was a less-than-technical term for cave dwellers. The name of the Troglytes on Ardana was also derived from the term. (TOS: "The Cloud Minders")
The 20th century Earth cartoon, Daffy Duck and the Dinosaur, featured a caveman named Casper, who lived in a cave with a "welcome" mat in front. (VOY: "Memorial")
Two decades after Dramia II was first hit by an Dramia II plague, the once civilized planet again had cave dwellers. (TAS: "Albatross")
In 2365, upon studying an Iconian device recovered from Denius III, Donald Varley described his frustration at not understanding it by comparing him to a caveman confronted with a tricorder. (TNG: "Contagion")
In 2366, Jean-Luc Picard explained the differences between himself and the Mintakan Nuria by having her compare herself to her cave dwelling ancestors. (TNG: "Who Watches The Watchers")
After being stranded on Hanon IV, USS Voyager crewmembers speculated that its natives might be cave dwellers. (VOY: "Basics, Part I")
The Novans would also qualify as cave dwellers.