The Southern Sun is a generation ship, or a spacefaring vessel that contains a large number of people, whose mission is to colonize a new world. Its voyage has lasted generations, so many of its inhabitants have been born and will die without ever setting foot on solid ground. This does not please the antagonist, Elijah Kalgan, who conspires with the pirates infesting the nearby Corona Borealis system and the ship’s Chief Engineer MacPhearson.Kalgan hatches a plot to disrupt the Southern Sun’s navigation systems and use the Enforcers, the ship’s police force, to hijack the ship and direct it towards this system. The occupants of the Southern Sun will then have no choice but to submit to Kalgan's leadership. Kalgan sabotages a key part of the ship just as an important professor's shuttle is on a landing trajectory. The loss of guidance control causes the ship to explode. The shuttle's pilot, Dave Ryder, is able to escape, but the professor dies in the explosion.
This sabotage seals off the flight deck for a number of weeks, which gives Kalgan the opportunity to attempt to wrest control. With the Enforcers in his hand, and with the flight deck out of commission, he holds the entire population of the Southern Sun hostage. Commander Jansen and Captain Devers enlist Ryder’s assistance, aided begrudgingly by Jansen’s daughter Dr. Lea Jansen, to regain control of the ship. .
During this conflict a number of characters meet with untimely ends due to railing kills.
- Reb Brown as Dave Ryder
- John Phillip Law as Kalgan
- Cameron Mitchell as Alex Jansen
- Cisse Cameron as Lea Jansen
- Graham Clarke as Scott Devers
- James Ryan as MacPhearson
- A prominent member of the Southern Sun's bridge crew is killed during a bar scene in an apparent attempt to make the plot more interesting. However, she is in the next scene alive and well at her console on the bridge. No mention is made of any twins (though, to give the movie the benefit of the doubt, she's only briefly seen in the foreground and is not featured again after her death).
- The space-battle footage is all lifted from the TV series Battlestar Galactica (1978).  The SOL crew do not comment on this during the episode, but mention of it was made later on the MST3K section of the Sci-Fi Channel website. The BBI staff apparently did not recognize the footage as being recycled until after the episode aired.
- Two of Cameron Mitchell's children had bit parts in this movie. His son Chip played the thinly mustached Blake who apologizes for the "scanty" information. His daughter Cammile was the voice of the lead Bellerian, Jennera.
- Actor James Ryan, who is the object of several jabs by the SOL Crew for his rather well-done (yet vaguely psychotic) performance as one of the two villains, starred in many similarly low-budgeted South African productions like this.
- Reb Brown and Cisse Cameron are married in real-life and were already a wedded couple when Space Mutiny was filmed. Contrary to the SOL crew's jokes, Cameron is a few years younger than Brown.
- Cisse Cameron would later claim that Space Mutiny was intended to be a spoof of science fiction films.
- RiffTrax presented Space Mutiny live on June 14, 2018. This presentation featured new jokes and new nicknames for David Ryder. (Flex Limpshaft, Burpee McCrossfit, Crash McPunchFace, Gunner Battlepants...)