Miguel de Cervantes wrote Don Quixote in Spanish, specifically the Early Modern Spanish of the seventeenth century. The novel’s original language is therefore Spanish, not French, Italian, or Portuguese.
The first part, published in 1605, introduces Alonso Quixano, a country gentleman who reads so many chivalric romances that he believes he has become a wandering knight. Calling himself Don Quixote, he sets out with the practical Sancho Panza, producing comic encounters that repeatedly expose the gap between fantasy and reality.
Cervantes published a second part in 1615. Together, the two parts are widely regarded as foundational works of the modern European novel. The book is famous for its layered narration, parody of medieval romances, shifting viewpoints, and playful treatment of authorship and translation.
The title character’s name is usually rendered as “Don Quixote” in English, while modern Spanish commonly uses “Don Quijote.” English readers may also encounter different translations because translators make varied choices about archaic language, humor, and wordplay. Those translation differences do not change the original language.