The film tells the story of Plant Spaceball's mission to extract all of the air from the neighbor planet Druidia. Their plan is to kidnap the Druish Princess Vespa, who is about to marry the narcoleptic Prince Valium. In protest of their marriage Princess Vespa runs from the alter with her Droid of Honor, Dot Matrix, and escapes into space, where she is attacked by the Spaceballs under the command of Dark Helmet.
Upon discovering Dark Helmet's plans to kidnap his daughter, King Roland requests the help of Lone Starr and his mawg (half-man, half-dog) sidekick, Barf, who are desperate for money to pay back their debts to Pizza the Hutt. Lone Starr and Barf eventually rescue Princess Vespa and Dot Matrix (through a series of fights involving light saber like weapons) and destroy the Spaceball ship. In the process, Princess Vespa and Lone Starr fall in love, only to discover that Lone Starr is in fact a prince. In the end the two marry and live happily ever after.