Dulcinea del Toboso is Don Quixote's lady, and she is his invention: a farm girl named Aldonza Lorenzo, to whom the gentleman thought it fitting to give the title of lady of his thoughts and a princess's name, taken from her village, El Toboso.
Chapter I recounts the christening: he looks for a name that matches his own and tends toward that of a princess and great lady, and he begins calling her Dulcinea del Toboso. He describes her to the knight Vivaldo in chapter XIII: the name is Dulcinea, the homeland El Toboso, her rank at least that of a princess, and her beauty superhuman, because in her all the impossible and chimerical attributes of beauty that poets give their ladies come true. In chapter XXV he tells Sancho that he paints her in his imagination as he wishes her to be, and in Part Two he confesses that he has never seen her and is in love with what he has only heard said of her.
In Part Two, Sancho, who did not carry the letter, points out three mounted farm women in El Toboso and says that one of them is Dulcinea, enchanted; the gentleman sees the farm woman and attributes the change to the enchanters (chapter X). The lie changes hands when the duchess tells Sancho that he is the one deceived, and the dukes provide him with a Merlin who demands three thousand three hundred lashes to disenchant her.
Dulcinea lives above all in the gentleman's words and in what is done in her name. When the Knight of the White Moon knocks him down, the gentleman yields his life but not his lady: "Dulcinea del Toboso is the most beautiful woman in the world, and I the most unfortunate knight on earth," he says from the ground (chapter LXIV of Part Two).