In the framing story, a man begins to read from a book "The Princess Bride" to entertain his sick grandson.
The story begins with the beautiful Buttercup who lives on a farm. Buttercup spends her days ordering around the farmhand, Wesley who responds only with "as you wish" despite Buttercup's unceasing rudeness. Eventually, Buttercup comes to develop feelings for Wesley after she understands that him saying "as you wish" is his way of telling her that he loves her. Though the two of them are now in love, Wesley leaves on a quest to seek his fortune with the promise that he will return and marry Buttercup. Buttercup swears to be faithful but is devastated to learn that Wesley's ship has been attacked by the infamous Dread Pirate Roberts and presumes him to be dead.
Five years later Buttercup agrees to marry Prince Humperdinck even though she still loves Wesley. Before the wedding, Buttercup is kidnaped by three bandits (a Sicilian boss named Vizzini, a giant named Fezzik and a Spanish swordsman named Inigo who is seeking to avenge his father's murder). It is revealed that Humperdinck hires the trio to murder Buttercup in the enemy land of Guilder in order to give Humperdinck false pretext to wage a war.
A man in black is seen following the trio from a distance and Vizzini orders Fezzik and Inigo to kill him. The two fail and the stranger catches up to Vizzini and Buttercup and even defeats him in a battle of wits by tricking him into drinking poison, leaving him and Buttercup alone.
Buttercup believes the stranger to be the Pirate Roberts and pushes him off a hill in order to escape. As the stranger rolls down the hill he shouts "as you wish," thereby revealing himself to actually be Wesley. Buttercup follows him down the hill and the two are reunited. Wesley explains that though the pirate Roberts did in fact attack his ship, he took pity on Wesley's pleas for mercy and stories about Buttercup and instead befriended him and gave hymn the title of the Dread Pirate Roberts. The two of them begin to escape together but Humperdinck catches up to them and imprisons Buttercup and throws Wesley into a torture chamber. Humperdinck hurriedly marries Buttercup
Fezzik and Inigo reunite and discover that Count Rugen, Humperdinck's associate is the six-fingered man that Inigo is seeking to kill. Fezzik and Inigo decide to save Wesley because they believe they need his help to avenge Count Rugen. Wesley, Fezzik and Inigo break into the castle and kills Rugen. Wesley finds his way to Buttercup and stops her from killing herself by pointing out that her marriage is void because she did not say "I do." Wesley ties Humperdinck to a chair and escapes with Buttercup with Fezzik and Ingio in tow.
In the framing story, the grandson asks his grandfather to read him the story again tomorrow.