Irony, in its basic form, is a literary device or technique authors use to demonstrate how events are not always as they seem. In The Canterbury Tales, Geoffrey Chaucer (c. 1343–1400) uses this technique to show his readers that physical appearances often differ dramatically from reality. Within the overall description of a spiritual journey by a group of pilgrims, he frames his tales as separate stories told by the travelers to Canterbury.

Each of the author’s stories carries the ironic thread of appearance versus reality. Chaucer uses dramatic irony to point out how his characters’ deceptions warn his readers to be aware that the expected outcomes in each story might not be exactly what they foresee.

For example, in "The Knight’s Tale,” two young knights, Palamon and Arcite, engage in a bitter argument from their prison quarters over the right to love Emelye who they see planting flowers in her garden. Palamon escapes from the prison, and Arcite is eventually released and disguises himself to get close to Emelye by working for her family. The two meet up again in a grove and begin fighting. The fight is interrupted by the Duke Theseus who arranges to set up a tournament to decide who will marry Emelye. Unfortunately for the knights, Emelye has no desire to wed until she finds the man she truly loves. At the tournament, Arcite is the victor and wins Emelye’s hand. However, Arcite suffers a fall from his horse and is mortally wounded, but he reconciles with Palamon before his death. As a result, the Duke chooses Palamon to wed Emelye:

And thus with alle blisse and melodye
Hath Palamon y wedded Emelye

For now is Palamon in alle wele,
Lyvynge in blisse, in richesse, and in heele,
And Emelye hym loveth so tendrely,
And he hire serveth so gentilly,
That nevere was ther no word hem bitwene

Of jalousie or any oother teene.
Thus endeth Palamon and Emelye

Chaucer ironically demonstrates that life is unpredictable. He shows his readers that physical appearances might lead to physical attractions, but twists and turns often bring unexpected results.

Another example of Chaucer’s use of irony is found in "The Pardoner’s Tale.” In "The Pardoner’s Prologue,” the reader discovers that the Pardoner is not what he appears to be. Although he is a good preacher, he is a greedy hypocrite, motivated by money, who sells his pardons at the end of his sermons. Ironically, his theme is always the same: greed is the root of all evil.

My theme is alwey oon, and evere was—
Radix malorum est Cupiditas.

In "The Pardoner’s Tale,” three young men hear of their friend’s death. They decide to track down Death and kill him. The men find an old man during their search and once again Chaucer presents his theme of appearances versus reality. The Old Man is Death himself. The men are told that Death is under a nearby tree. At the tree’s bottom, they find bushels of gold coins which they decide to divide among them. To celebrate, one man goes off to get food and wine. However, he poisons one of the bottles. When he returns, the other two kill him in order to divide his share. Then, they drink the wine and end up poisoning themselves. Ironically, they found Death, and the Pardoner’s story is consistent with the theme of his sermons: greed is the root of all evil.

In The Canterbury Tales, Chaucer effectively uses irony to support the theme that we should not judge people by their appearances.

There are numerous examples of dramatic irony in The Canterbury Tales. Overall, Chaucer skillfully uses irony as a way of putting distance between what appears on the surface to be the case and what he thinks is really going on. Right from the outset, Chaucer adopts the literary strategy of drawing a clear distinction between Chaucer the (somewhat naive) pilgrim, the narrator of the Tales, and Chaucer the author of those very same Tales, a world-weary, cynical chronicler of human foibles, forever casting a knowing wink at the reader.

The pervading sense of irony is much in evidence in The General Prologue. Here, we are treated to a collection of character sketches of each individual pilgrim that develops Chaucer's taste for irony to its fullest extent. Chaucer, the naive pilgrim narrator has, it appears, many a good word to say about his fellow pilgrims as they gather together at The Tabard Inn. However, upon on closer inspection, we find that things are not all that they seem. The monk, for example, is lauded as "A manly man, to been an abbot able." On a superficial level, this is high praise indeed. However, Chaucer the ironist arguably wants to suggest, ever so gently, that worldliness (rather than piety) is the ideal qualification for becoming an abbot.

This is one of many examples of Chaucer using irony as a means of satirizing the Church. Here we see that there is a serious side to Chaucer's use of irony. Though a devout Christian, Chaucer nonetheless subscribed to a widely-held conviction in the Middle Ages that the Church was irredeemably worldly, hypocritical, and corrupt. Irony in The Canterbury Tales is not simply used for comic effect; it has a clear moral purpose too.

Both comic and moral elements are ably combined in the amply proportioned figure of the Prioress. Chaucer the naive pilgrim gazes admiringly at her flashy jewels, including a "brooch of ful gold shene." Yet, Chaucer the ironist cannot resist insinuating that such ostentatious displays of wealth are rather inappropriate for the head of a nunnery.

Chaucer's irony, though, is never intended to be wounding or vicious. Even the Prioress, for all her obvious faults, still proves to be an immensely stimulating companion on the long, arduous journey to Canterbury. In other words, for all its importance as a literary device, irony is never allowed by Chaucer to obscure his unforgettable, sympathetic portrait of fallen humanity in all its richness and diversity.