The Quest for El Cid is a nonfiction book by Richard Fletcher. The titular historical figure is the Castillian hero Rodrigo Diaz del Vivar, who is known by the nickname "El Cid". The main theme of the book is discerning the mythology of historical figures—one in which El Cid is seen as a medieval hero in the Spanish collective consciousness—and their realistic portrait, which in this case is Rodrigo Diaz del Vivar. Fletcher examines how mythologies or legendary stories develop and how accurate they are in contrast to the documented facts about a historical figure's life.

Another theme of the book is the influence of patriotism in portraying historical figures in the context of Spanish history and identity. Fletcher, unlike the Spanish historian Ramon Menendez Pidal, analyzes El Cid's life and personality from an objective point of view. In this sense, The Quest for El Cid is also about the methodology of historical scholarship. Fletcher constructs this biographical work by separating fact from folklore, because little is known about the personal life of El Cid.

Another theme of the book is the documentation of Spanish life—especially during the height of The Kingdom of Castile—which offers a glimpse of other historical figures during El Cid's era.