Othello the Moor, a general employed by the Venetian state, has secretly married Desdemona, a daughter of the senator Brabantio.
Iago, a lower-ranking officer, nursing resentment against Othello, enlists the help of Rodorigo, a disappointed suitor of Desdemona. They wake Brabantio in the middle of the night with the news of his daughter's elopement. Brabantio takes the case to the senate where, learning that she has married Othello of her own accord, he disowns his daughter. Othello is immediately ordered to the Venetian colony of Cyprus to repel a threatened Turkish invasion. Desdemona sails with her husband, taking with them her companion Emilia, who is also Iago's wife, and Othello's lieutenant Michael Cassio, newly-promoted instead of Iago.
Once in Cyprus, Iago plants the suspicion in Othello's mind that Desdemona has been unfaithful to him with Cassio. He engineers a drunken brawl for which Cassio is blamed and dismissed by Othello. Desdemona intervenes on Cassio's behalf but her pleas to Othello for his reinstatement simply convince Othello further that Cassio is her lover.
The plot unravels
Iago acquires a treasured handkerchief that belonged to Desdemona and uses it as 'proof' of the affair. Increasingly maddened by jealousy, Othello orders Iago to kill Cassio and smothers Desdemona himself. Emilia discloses her husband's plot and Othello, tormented by grief and remorse, kills himself. Iago, after murdering his own wife, is left to the justice of the Venetian state.