In Venice and then in Cyprus, the Moorish general Othello, in the service of the Signoria, marries Desdemona, daughter of the senator Brabantio. His ensign Iago, who feels passed over, decides to destroy him, and the play tells in five acts how he leads him to believe that his wife is betraying him with the lieutenant Cassio, until Othello kills her and discovers the truth too late.
Act I
On a Venetian street, at night, Iago and Roderigo, who wants Desdemona for himself, wake Brabantio with shouts to warn him that his daughter has run off with the Moor. Iago confesses to Roderigo that he hates Othello for giving the lieutenancy to Cassio and that he serves him only out of convenience (scene 1). Iago warns Othello that Brabantio is powerful and can undo the marriage; Othello refuses to hide, Cassio brings the Duke's urgent summons, and Brabantio arrives armed to arrest him for witchcraft. Othello defuses the confrontation, and everyone heads for the Senate (scene 2). There, at night, the Duke and the senators conclude that the Turkish fleet is heading for Cyprus. Brabantio accuses Othello of having won his daughter with potions and spells, and Othello answers by recounting his own life and how Desdemona loved him for it. Desdemona confirms the marriage and declares her duty divided between her father and her husband. The Duke orders Othello to leave for Cyprus that very night, and Othello names Iago as Desdemona's escort, with the Duke's approval. Alone, Iago convinces Roderigo to sell his lands and follow to Cyprus, promising to help him win Desdemona, and plans to exploit Othello's frankness (scene 3).
Act II
In Cyprus, Montano and the gentlemen watch the raging sea from the quay and conclude that the Turkish fleet has been lost in the storm. Cassio arrives first, then Desdemona with Iago and Emilia, and last Othello, who is reunited with his wife in the midst of joy. Iago mocks women, arranges with Roderigo to provoke Cassio during the watch, and reveals, alone, that he wants to destroy Cassio and Othello (scene 1). A herald proclaims the destruction of the fleet and a night of feasting for the victory and the marriage (scene 2). Othello puts Cassio on watch and withdraws with Desdemona. Iago makes Cassio, who knows he is weak with drink, drink with Cypriots; Roderigo provokes him, Cassio wounds Montano, and Othello, woken by the tumult, strips him of the lieutenancy. Crushed by the loss of his reputation, Cassio hears from Iago the advice to ask Desdemona for help, and Iago, alone, says he will weave a net for the three of them (scene 3).
Act III
Cassio pays musicians to greet the general at dawn and, through Emilia, reaches Desdemona (scene 1). Othello goes out to inspect the fortifications (scene 2). Desdemona promises Cassio to defend him, and when Othello arrives with Iago and Cassio hastily withdraws, Iago insinuates doubts, first merely by echoing and suggesting, but already with a "Nothing, my lord" that is a lie. Desdemona drops the handkerchief Othello had given her; Emilia finds it and hands it to her husband, who had asked her many times to steal it. Othello demands ocular proof, and Iago answers with a dream attributed to Cassio and with the strawberry handkerchief with which he says he saw Cassio wipe his beard. Othello swears vengeance and names Iago lieutenant (scene 3). Desdemona notices the missing handkerchief, and Othello, when he asks for it, tells of its magical origin and storms out demanding it, while she insists on speaking of Cassio. Emilia says what she thinks of men, and Cassio gives the handkerchief to Bianca so that she can copy the pattern (scene 4).
Act IV
Iago speaks to Othello of "handkerchief" and of "lying" until he, repeating "the handkerchief, the confessions," falls into convulsions. Back on his feet, Othello hides to hear Iago talk with Cassio about Bianca, takes Cassio's laughter for a confession about Desdemona and, on recognizing the handkerchief, decides to kill her; Iago suggests strangling. Lodovico arrives from Venice with the letter that calls Othello back, and Othello strikes Desdemona in front of him (scene 1). Othello questions Emilia, who swears to her mistress's honesty, and treats Desdemona as a whore. Iago comforts Desdemona and then restrains Roderigo, who demands the jewels, promising him a night of action against Cassio (scene 2). Desdemona asks that, if she dies, they wrap her in the wedding sheets, sings the willow song and talks with Emilia about whether a wife would betray her husband, and Emilia says the fault lies with the husbands (scene 3).
Act V
On a dark street in Cyprus, Iago posts Roderigo to kill Cassio and admits in an aside that the death of either of them suits him. Roderigo misses his blow and Cassio wounds him; Iago, from behind, cuts Cassio's leg and flees. Othello, from afar, takes the cries as a sign that Iago has kept his word. Iago returns as a rescuer, kills Roderigo and accuses Bianca (scene 1). In the bedchamber, Othello kisses the sleeping Desdemona, accuses her of having given the handkerchief to Cassio and smothers her; she denies it to the end and, with her last breath, says it was she herself. Emilia arrives, hears from Othello that Iago informed him, and unmasks her husband: it was she who found the handkerchief and gave it to him. Iago kills her and flees. Captured, he falls silent; letters found in Roderigo's pocket clarify the plot, and Othello, after asking that they speak of him as he is, kills himself beside Desdemona. Cassio is left in command of Cyprus (scene 2).