Othello's Lieutenant is a term used to refer to two characters in William Shakespeare's play Othello. The first is Cassio, a Florentine soldier who is appointed by Othello as his lieutenant. He is a young, inexperienced man who is loyal to Othello and is ultimately wrongfully accused of infidelity. The second is Iago, a Venetian soldier who is Othello's ensign. He is a manipulative and deceitful character who plots against Othello and Cassio in order to gain power and revenge.