The Canterbury Tales is one of the landmarks of English literature, perhaps the greatest work produced in Middle English and certainly among the most ambitious. It is one of the few works of the English Middle Ages that has had a continuous history of publication. It was the last of Geoffrey Chaucer's works, written after Troilus and Creseyde during the final years of Chaucer's life. Chaucer did not complete the entire Canterbury Tales as he designed it. He structured the tales so that each pilgrim would tell four tales, leading to a total of over one hundred tales. However, Chaucer only completed twenty-four tales, not even completing one tale for each pilgrim.

The Canterbury Tales includes a number of tales that Chaucer had written before creating the grand work itself. The Second Nun's Tale and the Knight's Tale were included as part of Chaucer's biography in the prologue to The Legend of Good Women, a poem by Chaucer that predated The Canterbury Tales, but since those stories survive only as part of The Canterbury Tales and not as independent works, it is impossible to determine whether Chaucer transferred them entirely to The Canterbury Tales or adapted them from a previous form.

The versions of The Canterbury Tales that remain in the present day come from two different Middle English manuscripts known as the Ellesmere and the Hengwrt manuscripts. The Ellesmere is the more famous of the two, containing miniature pictures of each of the pilgrims at the head of each of their respective tales, but compared to the Hengwrt manuscript the Ellesmere is heavily edited for grammatical content. The Hengwrt is thus valued as the best and most accurate manuscript of The Canterbury Tales. There are discrepancies between the two versions concerning the order and inclusion of the tales. The Hengwrt manuscript lacks the Canon's Yeoman's Prologue and tale, part of the Parson's Tale, and several of the tales' prologues.

The structure of The Canterbury Tales is indebted to Boccaccio's Decameron, a work by Chaucer's contemporary in which ten nobles from Florence, to escape the plague, stay in a country villa and amuse each other by each telling tales. Boccaccio had a significant influence on Chaucer. The Knight's Tale was an English version of a tale by Boccaccio, while six of Chaucer's tales have possible sources in the Decameron: the Miller's Tale, the Reeve's, the Clerk's, the Merchant's, the Franklin's, and the Shipman's. However, Chaucer's pilgrims to Canterbury form a wider range of society compared to Boccaccio's elite storytellers, allowing for greater differences in tone and substance.

No single literary genre dominates The Canterbury Tales. The tales include romantic adventures, fabliaux, saint's biographies, animal fables, religious allegories and even a sermon, and range in tone from pious, moralistic tales to lewd and vulgar sexual farces. The form that Chaucer most often employs for his tale is the fabliau. These tales generally concern lower class characters; the standard form has an older husband whose younger wife has an affair with a man of flexible social status. This can be seen most accurately in the Miller's Tale, which strictly adheres to fabliau conventions. Throughout the tales, two major themes emerge: the first is the idea of the unfaithful wife that is employed not only in fabliau but other literary genres. The other is the idea of the patient and suffering woman, who is exalted for her steadfast behavior. Chaucer exploits this division between the female saint and the whore throughout The Canterbury Tales, with few tales whose plots do not center at least marginally around this distinction.