Act 1
Outside Otello's castle, during a violent storm, the townspeople of Cyprus anxiously watch as the ship carrying Otello, their general, fights its way to port. Otello brings news of victory over the Turks, and the people rejoice.
Roderigo pines over Desdemona, Otello's wife, and Iago reveals his hatred for the Moor.
Otello has promoted Iago's rival, Cassio, to the rank of captain, and lago seeks revenge. Hoping to trick Cassio, Iago gets him drunk, meanwhile suggesting to Roderigo that Cassio is also in love with Desdemona. At Iago's urging, Roderigo provokes Cassio into a fight. When Montano interferes in the fight, Cassio wounds him.
Otello arrives, and is angered to discover that Cassio has been involved in a brawl. His mood is soothed by the appearance of Desdemona. Alone together, they recall how they fell in love — Desdemona fascinated by Otello's adventures, Otello drawn to Desdemona for her compassion. His heart full of love and joy, Otello leads Desdemona back to their castle.
Act 2
In a hall in the castle, Iago urges Cassio to ask Desdemona to use her influence with her husband, persuading Otello to forgive Cassio for his misconduct. Cassio leaves, and Iago, denouncing God, declares his allegiance to the devil. Life, he says, is a stupid farce, and after death, there is nothing.
In the garden, just outside the hall, Cassio approaches Desdemona and her maid, Emilia, while Iago watches. When Otello arrives and sees Cassio with Desdemona, Iago stirs up the Moor's suspicions. Otello's mistrust and jealousy grow when Desdemona asks him to forgive Cassio, but he refuses her help and throws the handkerchief she offers him to the ground. Emilia picks it up, and Iago forces her to give the kerchief to him. Desdemona and Emilia leave, and Otello, rapidly losing his senses, demands that Iago furnish proof of Desdemona's faithlessness. Iago tells how he overheard Cassio talking in his sleep, swearing Desdemona to secrecy about their love. Iago also reports that Cassio has Desdemona's handkerchief, the kerchief Otello gave her. In a rage, Otello swears vengeance and Iago joins him in his vow.
Act 3
Iago goes off to lure Cassio into a trap, and Desdemona joins Otello. At first controlled, the Moor quickly loses his composure when Desdemona admits she does not have the handkerchief he gave her. Thinking Otello is trying to distract her from pleading for Cassio's case, she renews her request that Otello forgive Cassio. Otello, in growing fury, accuses Desdemona of faithlessness. Horrified, she denies his charges. He sarcastically apologizes and shows her out.
Alone, Otello laments his lost happiness. He resolves to force Desdemona's confession and then to kill her. At Iago's suggestion, Otello hides and watches as Iago talks with Cassio. When Cassio produces the handkerchief which Iago has planted in his room, Otello recognizes it as Desdemona's, and is convinced of her betrayal.
Lodovico arrives, bringing papers ordering Otello to return to Venice and appointing Cassio as Otello's replacement in Cyprus. His anger sparked, Otello verbally abuses Desdemona, who, already worn with anxiety over her husband's behavior, faints. All are shocked by Otello's ill treatment of his wife.
Iago advises Otello to strike quickly, and promises to dispatch Cassio. Approaching the love-sick Roderigo, Iago persuades him to wound Cassio —thus forcing Otello, a nd so, Desdemona, to stay in Cyprus.
After everyone has gone, Otello, in the grip of a fit, collapses. Iago stands in victory over him.
Act 4
In her bedroom, Desdemona remembers a sad song and bids her maid Emilia goodnight. She prays before going to bed. Otello wakens his sleeping wife and confronts her. She denies his accusations and, even as she pleads for mercy, he suffocates her.
Emilia enters with the news that Cassio has killed Roderigo. Discovering that Otello has murdered Desdemona, Emilia calls for help. When Emilia reveals Iago's treachery, Otello realizes his mistake. He stabs himself, and dying, calls out to Desdemona for one last kiss.