A drama in five acts, performed about 1601-02 and printed in a quarto edition from a fair copy, possibly the author's, in 1609. Although this play is included among the tragedies in the First Folio, many critics prefer to classify it with the "problem plays" or the "dark" comedies. Based on George Chapman's translation of the Iliad and on 15th-century accounts of the Trojan War by John Lydgate and William Caxton, Troilus and Cressida is an often cynical exploration of the causes of strife between and within the Greek and Trojan armies--the betrayal of love, the absence of heroism, and the emptiness of honour. The play was also influenced by Geoffrey Chaucer's love poem Troilus and Criseyde, although Shakespeare's treatment of the lovers and his attitude toward their dilemma is in sharp contrast with Chaucer's.

It is the seventh year of the Trojan War, a Trojan prince named Troilus falls in love with Cressida, the daughter of a Trojan priest who has defected to the Greek side. Pandarus, Cressida's uncle, assists Troilus in his pursuit. Meanwhile, in the Greek camp, the Greeks besieging Troy are bickering amongst themselves, the Greek general, Agamemnon, wonders why his commanders seem so downcast and pessimistic. The wise and crafty Ulysses informs him that the army's troubles spring from a lack of respect for authority, brought about by the behaviour of Achilles, the greatest Greek warrior, who refuses to fight and instead spends his time sitting in his tent with his comrade (and lover) Patroclus, mocking his superiors. Shortly thereafter, a challenge to single combat arrives from Prince Hector, the greatest Trojan warrior, to duel any Greek in one-on-one combat, and Ulysses puts the fix in on a lottery decides to have Ajax, a headstrong fool, fight Hector instead of Achilles, Ulysses hopes to spur the pride of Achilles by slighting him in the matter.

Meanwhile, in Troy, the sons of King Priam debate whether it is worthwhile to continue the war--or whether they should return Helen to the Greeks and end the struggle. Hector argues for peace, but is eventually won over by the impassioned Troilus. In the Greek camp, Thersites, Ajax's foul-mouthed slave, abuses everyone who crosses his path. His master, meanwhile, is honoured by the commanders over the sulking Achilles, and is to fight Hector the next day.

That night, Pandarus brings Troilus and Cressida together, and after they pledge to be forever true to one another, he leads them to a bedchamber to consummate their love. Meanwhile, Cressida's father, the treacherous Trojan priest Calchas deserts Troy for the Greek encampment. He proposes a simple barter; in exchange for telling what he knows of the Trojan forces, the Greeks will exchange a Trojan prisoner for his daughter, Cressida. Agamemnon, commander of the Greek army, agrees to this, Troilus parts with Cressida, and Greek lord Diomedes leads Cressida away from Troy.

However, Cressida seems less concerned about their separation when she meets- and flirts-with all the Greek generals. Trumpets blare, and Hector arrives to duel with Ajax. The two men battle each other to a standstill and eventually call a truce. The Trojan and Greek generals will dine together that evening at a feast.

That afternoon, Ajax and Hector fight to a draw, and after Hector and Achilles exchange insults, Hector and Troilus feast with the Greeks under a flag of truce. As the camp goes to bed, Ulysses leads Troilus to the tent of Calchas, where the Trojan prince watches from hiding as Cressida agrees to become Diomedes's lover, seeing Cressida give Diomedes the sleeve that Troilus had given to her when she left Troy. He vows to kill Diomedes in battle.

The next day, in spite of unhappy premonitions from his wife, sister, and his father, Hector takes the field, and a furious and heartbroken Troilus accompanies him. The Trojans drive the Greeks back, Hector slays Patroclus, which brings a vengeful Achilles back into the war, finally. Achilles unable to defeat Hector in single combat, later catches him unarmed and, together with a gang of Greek warriors, slaughters him. Achilles then drags Hector's body around the walls of Troy, and the play ends with the Trojan warriors retreating to the city to mourn their fallen hero.

Troy has suffered a grave defeat by the end of the day, and an enraged Troilus hurls curses at Achilles and Pandarus alike.

The play is not a comedy because it does not end on a hopeful note, but it lacks the scope and intensity of a tragedy. The poet Samuel Taylor Coleridge remarked, "There is none of Shakespeare's plays harder to characterize."