Act I
On a stormy night, the people of Cyprus are gathered on the seashore, awaiting the return of their new Governor, Otello after a battel with the Turks. In a flash of lightning, Otello's ship appears to sink, but it reaches the shore safely. Otello announces that the Turkish fleet is destroyed. The Cypriots celebrate by drinking and lighting fires on the shore to commemorate the victory. However, Otello's ensign, Iago, does not share their joy. He harbors treachery in his heart, envying Otello's success and plotting to destroy him. Additionally, Otello promoted a young, handsome officer, Cassio as the fleet's captain. Iago wanted this promotion for himself.

Iago starts to put his plan into action. He offers his assistance to the young Venetian, Roderigo, to win Desdemona, Otello's wife. Knowing the weaknesses of those around him, Iago intends to exploit these to his advantage. He joins the festivities, toasting to Otello and Desdemona. Cassio, praises Desdemona, his old friend. Iago persistently urges Cassio to drink wine. Cassio refuses in the beginning but eventually gives in and becomes very drunk.

Montano, the former governor of Cyprus, enters to remind Cassio that his watch is starting. He finds Cassio drunk and barely able to stand upright. Iago lies to Montano, slandering Cassio by claiming that he is drunk every night. Roderigo mocks Cassio's drunkenness, and Cassio draws his sword. Montano tries to stop the fight, but Cassio turns on him. Montano is wounded. The fight is abruptly ended by Otello's arrival.

Otello asks Iago to report on what happened, but Iago feigns ignorance. Embarrassed, Cassio cannot justify his actions, and Montano is wounded. The commotion awakens Desdemona, who rushes to the scene. Enraged by the disorder, Otello demotes Cassio from his captaincy and commands Iago to restore peace in the city. He then orders assistance for Montano and instructs the assembled crowd to disperse.

Otello and Desdemona are left alone. At the peak of bliss, Otello declares he is ready to die for this love and happiness, while Desdemona prays to God that their love will never waver.

Act II
Iago meets Cassio and, pretending to be helpful, advises him to ask Desdemona to plead with her husband for his reinstatement as captain, taking advantage of the opportunity now that Desdemona and Emilia are walking in the garden. Cassio, believing Iago, approaches Desdemona. Left alone, Iago reveals his true intentions and 'belief'.

Otello enters. Iago pretends not to see him and starts to sigh. When Otello questions him, Iago hesitantly suggests that Desdemona is betraying him with Cassio. This plants a seed of suspicion in Otello’s heart, yet he demands proof of her betrayal. Iago cautions him against harboring suspicions, at the same time, advises him to remain vigilant.

A chorus of Cypriots sings songs of praise for Desdemona, presents gifts, and wishes her happiness.

Desdemona conveys to Otello Cassio's regrets and his wish to be reinstated. Otello is unwilling to discuss it, but Desdemona persists. Otello complains of a headache. When Desdemona offers to bind his head with a handkerchief embroidered with strawberries, which he had gifted her, Otello declines, saying, 'I don't need it,' and throws the handkerchief away. Emilia, Desdemona's maid, picks up the handkerchief. Desdemona seeks Otello's forgiveness. Quietly but persistently, Iago demands the handkerchief from Emilia and ultimately takes it by force.

Otello believed in Desdemona's betrayal, but he still wanted proof. Iago enters and tells Otello how he once, by chance, overheard Cassio speaking in his sleep. As if in a dream, Cassio addressed Desdemona, warning her to conceal their love. Iago also mentions that he saw Cassio with Desdemona's handkerchief, embroidered with strawberries, just the day before. Otello and Iago swear revenge.

Act III

In the great hall of the castle, a herald brings news of the approach of the Venetian ambassadors. Iago suggests to Otello that he will lure Cassio to the hall and talk with him, while Otello hides and listens.

Before Cassio's arrival, Desdemona enters the hall and reminds Otello of Cassio's request. Otello asks her to wrap his head with a handkerchief embroidered with strawberries to ease his pain. Desdemona does not have this handkerchief with her, and Otello warns that it is a talisman of their love, and losing it would bode ill. Despite this, Desdemona repeatedly returns to the topic of Cassio. With equal persistence, Otello demands the handkerchief and gradually brings up the subject of betrayal. Astonished, Desdemona insists on her faithfulness, but Otello refuses to listen to anything and sends her away.

Meanwhile, Iago brings Cassio in. Otello hides out of sight. Cassio mentions he hoped to meet Desdemona there to inquire if she had made any progress with Otello on his behalf. Iago then leads him away, ensuring their conversation only reaches Otello in fragments. Quietly, Iago inquires about Cassio's lover, Bianca. Cassio responds cheerfully, and Otello concludes they are discussing Desdemona. Amidst the difficult-to-discern conversation, Cassio mentions a handkerchief left by an unknown admirer and shows it to Iago as proof of his story. Iago abruptly snatches it away, making sure Otello sees it, before quickly hiding it again and continuing to rattle on, while Otello, humiliatingly hidden, is seething with rage alone.
The Venetian ambassador, Lodovico, arrives. Iago escorts Cassio out of the hall and discusses with Otello different methods to kill Desdemona. The decision is made to kill Desdemona by suffocating her in her bed. Otello then promotes Iago to the rank of Captain, a position previously held by Cassio.

Accompanied by Desdemona, Emilia, Roderigo, and other dignitaries, Lodovico inquires about Cassio. According to Iago, Cassio is no longer a welcome guest. Desdemona expresses hope that this situation will not last longg and that Cassio will soon be reinstated. Her comment shocks Otello, who denounces his wife as a demon and, amidst a barrage of insults, moves to strike her. The arrival of Cassio coincides with the disclosure of the Doge of Venice's letter: Otello is ordered to return to Venice, and Cassio is appointed the governor of Cyprus. This news is the final blow to Otello's patience. In a rage, he throws Desdemona to the ground. Emilia and Lodovico try to comfort her, while Roderigo is concerned about her imminent return to Venice. Iago quietly urges Otello to seek revenge as soon as possible, adding that he will take care of Cassio himself. Later, he meets a distraught Roderigo and convinces him that to prevent Desdemona's departure, he must kill Cassio by all means.

Enraged, Otello orders everyone to leave. Desdemona's attempts to calm him are in vain. Instead, her efforts only fuel Otello's fury and Desdemona is being led away by Lodovico. With his mind in turmoil, Otello collapses. Iago approaches, placing his foot on Otello's head in a gesture of victory, as if intending to crush him with his heel, and then walks away.

Act IV

An extremely saddened Desdemona prepares for bed. She asks Emilia to lay out the bridal gown she wore on her wedding day, stating that if she dies, she wishes to be buried in it. Desdemona then recalls how her mother's servant, Barbara, who was abandoned by her lover, used to sing the mournful Willow Song and how she passed away. After Emilia departs, Desdemona prays and then falls asleep.

Otello enters silently with a sword in his hand and, upon seeing his sleeping wife, is seized with momentary tenderness, kissing her three times. Desdemona wakes up. Otello asks if she has prayed before going to sleep because he is about to end her life and does not want her immortal soul to perish. Realizing that all pleas are in vain, Desdemona asks God for mercy for both herself and her husband. Otello accuses her of betrayal with Cassio, but Desdemona denies the accusation and, to prove her innocence, asks Otello to bring Cassio. Otello believes Cassio is already dead. Desdemona's final attempt to win her husband's pity is in vain. Following Iago's advice, Otello strangles her in bed.

Emilia persistently knocks on the door, bringing news that Cassio has killed Roderigo. As she dies, Desdemona whispers that she has been unjustly punished, asserting her innocence, yet she does not blame Otello. Emilia calls Otello a murderer, and Otello responds that he had reason to believe in Desdemona's betrayal - the handkerchief that Iago brought to him. As Emilia starts to shout, Iago, Cassio, and Lodovico enter. Otello claims that the strawberry-embroidered handkerchief Desdemona gave to Cassio is proof of her infidelity. A distraught Emilia explains to Otello that she found the handkerchief and that Iago took it by force, and Cassio says he is unaware of how it came into his possession. Montano confirms what they say and states that Roderigo revealed Iago's plot before dying. Iago then flees.

Otello finally realizes what has happened. He grieves over Desdemona's death, longing to join her in death as soon as possible. He attempts to take his own life with his scimitar, but those present intervene and take the sword away from him. Undeterred, Otello fulfills his intention with a dagger. Before he dies, he drags himself next to his wife, kisses her as he did on the night of his arrival in Cyprus, and dies lying beside Desdemona.