Don Quixote is the title character of Spanish author Miquel de Cervantes' novel, fully titled, in translation, "The Ingenious Gentleman Don Quixote of La Mancha." The novel was published in two volumes, in 1605 and 1615 respectively, and is widely regarded as a founding work of modern literature.
Quixote is a middle-aged gentleman who becomes enchanted with the idea of chivalry and decides to go in search of adventure. He is frequently delusional, mistaking windmills for giants and grazing sheep for a marauding army. The expression "tilting at windmills" is a reference to Quixote's pointless, but well-meaning nature, as is the word "quixotic," meaning both overly chivalrous or romantic, but also impractical, unrealistic or hopeless.