Antonio is a sea captain. Though considered a pirate by Illyrians, he considers himself an honorable opponent.
Though due to his history of capturing Illyrians ships, he is not very welcome in Orsino’s lands, he knows which is the best inn in town. He is deeply infatuated with Sebastian, whom he saved from drowning, to the extent of following him to Illyria despite the personal danger to him. He is shocked and wounded when Sebastian (as he thinks) later refuses to acknowledge knowing him, let alone having borrowed his purse. When the real Sebastian rushed up to embrace him and return his money, he is deeply confused, and incapable of telling the difference between the twins. What happens to Antonio, who discovers that Sebastian has been married since they last saw each other that afternoon, is uncertain. Generally he joins in with the reveling, if in a bit of a lonely way; but it is not impossible that everyone forgets about him and that he’s executed after all.