Don Quixote begins with a prologue. Interestingly, much of this introduction is dedicated to pondering what a prologue should contain, offering readers insight into the expectations of a seventeenth-century audience while simultaneously challenging those very expectations.

Don Quixote narrates the tale of Alonso Quijano, an elderly gentleman from La Mancha. His excessive reading of chivalric romances drives him to madness. As the narrator describes: "With virtually no sleep and so much reading, he dried out his brain and lost his sanity."

Determined to become a knight-errant, Alonso dons an old suit of armor, mounts a frail horse he names Rocinante, and adopts the name Don Quixote de La Mancha. He chooses a local peasant woman, Aldonza Lorenzo, as his lady love, renaming her Dulcinea del Toboso. Emulating the knights of old, Don Quixote performs noble deeds in Dulcinea's name, despite her being unaware of his devotion.

Don Quixote embarks on his quest for adventure. Believing himself to be a knight, he mistakes a local inn for a castle and the innkeeper for a castellan. His delusions and peculiar actions result in a group of travelers beating him.

After this beating, he returns home, where the local priest and barber question him. Concerned for his well-being, they decide to cure his madness by burning his books. Don Quixote believes a thieving wizard has stolen them.

Soon, Don Quixote sets off on another adventure, this time with Sancho Panza, a crude peasant. In a well-known scene, Don Quixote confuses windmills for giants and charges at them with his spear. Upon realizing his mistake, he claims the same magician who stole his books transformed the giants into windmills.

Don Quixote and Sancho experience several more misadventures, including mistaking two herds of sheep for armies and a funeral procession for a parade of monsters. They also free prisoners on their way to becoming galley slaves. Don Quixote retreats to the mountains to fast and pray for his love, Dulcinea, and sends Sancho Panza with a message for her. Don Quixote's friends intercept Sancho and discover his master's location. They eventually lure Don Quixote back home, hoping to keep him safe.