The Phantom Empire is a 1935 American Western serial film directed by Otto Brower and B. Reeves Eason and starring Gene Autry, Frankie Darro, and Betsy King Ross.

The serial film is about a singing cowboy who stumbles upon an ancient subterranean civilization living beneath his own ranch that becomes corrupted by unscrupulous greedy speculators from the surface.

A chance to become real heroes occurs when Betsy, Frankie, and Gene are kidnapped by the real Thunder Riders from the super-scientific underground empire of Murania, complete with towering buildings, robots, ray-guns, advanced television, elevator tubes that extend miles from the surface, and the icy, blonde, evil Queen Tika (played with relish by Dorothy Christie).

The inhabitants of Murania are the lost tribe of Mu, who went underground in the last glacial period 100,000 years ago, and now live in a fantastically advanced city 25,000 feet below the surface.

Fred Olen Ray in 1988 filmed a movie called The Phantom Empire about treasure hunters braving a cavern system populated by troglodytes and other subterranean hazards to finally encounter an underground lost civilization.

The UK Channel 4 show Exploitica lampooned the serial, adding comedic sound effects, thought bubbles and captions to each episode.

Most notably, one 2020 storyline in Funky saw Jeff and his grandson seeking refuge from a wildfire in the cave used for the film as the entrance to Murania, where they imagine being rescued by the Thunder Riders and taken into the city.