Michael Cassio, or simply Cassio, is a fictional character in William Shakespeare's Othello. The source of the character is the 1565 tale "Un Capitano Moro" by Cinthio; Cassio is unnamed in Cinthio but referred to as "the squadron leader". In the play, Cassio is a young and handsome lieutenant under Othello's command who becomes one of Iago's several victims in a plot to ruin Othello.