Iago, Venetian army officer and ensign to the Moorish general, Othello, bitterly resents the appointment of Cassio as Othello's lieutenant. Roderigo and Iago maliciously bait Brabantio, an old senator, with the news that his daughter Desdemona is betrothed to Othello. Before Council Chamber, Brabentio accused Othello of abducting his daughter. The Moor denies this, and Desdemona affirms loyalty to her husband. Othello is ordered to defend Cyprus, of which he is Governor, against the Turks. Iago assures Roderigo, who is secretly in love with Desdemona, that she will not love Othello for long. Iago brings Desdemona to Cyprus to celebrate Othello's victory against the Turks and incites Cassio and Montano into a drunken brawl. Montano is seriously hurt and Iago beckons Othello, blaming Cassio, who is dismissed from duties. Iago then advises Cassio to seek Desdemona's assistance in regaining Othello's favor. Iago arranges Othello to find his wife in earnest conversation with Cassio, and subtly arouses the Moor's jealousy with creating a slanderous piece of evidence by placing Desdemona's handkerchief in the possession of Cassio.

This is the only Shakespeare film in which all four leading actors (Laurence Olivier, Maggie Smith, Frank Finlay and Joyce Redman) were nominated for Oscars.

Iago:
O beware my lord,of jealousy! It is the green-ey'd monster which doth mock the meat it feeds on.

Revealing mistakes: SPOILER: After Othello dies and Iago is taken away, when Lodovico passes by Desdemona's death bed, you can see Othello breathing still.