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. In the 2018 RiffTrax presentation, Mike Nelson quips, "Yes, we know it's the Battlestar Galactica, you nerds," acknowledging that MST3K missed it and the reaction from fans that was prompted by the oversight.
- 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 played MacPhearson) starred in many similarly low-budgeted South African productions. Some of his other films later became RiffTrax productions.
- There were three directors on this film. David Winters was the original director, but he had to leave the project in the early stages of production. Winters was replaced by Neal Sundstrom, who did most of the actual work of directing. After production finished, it was discovered the film was not long enough to classify as feature-length, so the scenes with the Bellarians were added. Neither Winters or Sundstrom agreed to direct those scenes, so David A. Prior did. David Winters attempted to have his name removed from the credits, but Sundstrom refused sole credit as director, as he was reportedly equally unhappy with the final project.
- 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, etc).