is a well-regarded Venetian merchant.
Interestingly, unlike the titles of Shakespeare's tragedies and histories, which are all named after the protagonist(s), of the fourteen comedies that Shakespeare wrote, only four titles—The Merchant of Venice, Taming of the Shrew, Two Gentlemen of Verona, and The Merry Wives of Windsor—refer directly to characters in the plays.
However, no one refers directly to Antonio as a merchant from Venice until well past the midpoint of the play:
GRATIANO: . . . What's the news from Venice?How doth that royal merchant, good Antonio? (3.2.244–245)
We learn in the very first scene of the play that Antonio is a well-respected merchant, and that he has many ships at sea:
SALERIO: Your mind is tossing on the ocean;There, where your argosies, with portly sail,—Like signiors and rich burghers on the flood,Or, as it were, the pageants of the sea,—Do overpeer the petty traffickers,That curt'sy to them, do them reverence,As they fly by them with their woven wings. (1.1.8–14)
Since Antonio has all of his money invested in his ships and merchandise, he's unable to lend his friend, Bassanio, the money he needs to hold his place with other suitors and respectably woo Portia.
BASSANIO: . . . For the four winds blow in from every coastRenowned suitors . . .O, my Antonio! had I but the meansTo hold a rival place with one of them,I have a mind presages me such thrift,That I should questionless be fortunate. (1.1.173–181)
Antonio agrees to let Bassanio borrow money in his name from Shylock, the money-lender and a hated adversary of Antonio, and the main plot of the play begins.
Present-day misperceptions about to whom the title of the play actually refers arise from the prominence of the Shylock character in the play. Shylock is a much more flamboyant and engaging character than Antonio, and, as in a number of Shakespeare's plays (and many other plays), the villains are much more interesting and memorable than the stalwart heroes.
In Shakespeare's time, the confusion about the title arose from two sources: a notation about the play in the Stationer's Register (where records of plays approved for publication were made), and the title of the first printed version of the play.
The entry in the Stationer's Register in 1598 reads: "a book of the Merchant of Venice, otherwise called the Jew of Venice." Although no existing published version of the play carries the title The Jew of Venice, the title The Merchant of Venice was thought to refer to Shylock, not to Antonio, even though Shylock is definitely not a merchant, but a money-lender, and not the protagonist in the play.
Adding to the confusion, Christopher Marlowe wrote a play in about 1589 entitled The Jew of Malta, in which the Jew of the title, Barabas, a villainous character (but considerably more villainous than Shylock), poisons his own daughter and nearly everyone else in sight, arranges for Turkish galley slaves and soldiers to be blown up by gunpowder, and devises a trap for the Turkish prince and his men to be boiled alive.
Given that a large number of playgoers in Shakespeare's time were anti-Semitic, even though many of them would never have met or even known a Jew in their entire lives, they would have cast Shylock and Barabas in much the same villainous mold and thought of the characters as interchangeable.
The first printed edition of the play in 1600 is titled The most excellent Historie of the Merchant of Venice. With the extreame crueltie of Shylocke the Jewe towards the sayd Merchant, in cutting a just pound of his flesh; and the obtaining of Portia by the choyce of three chests—which pretty much gives away the entire plot of the play.
Although the title clearly states that the play is about the "Merchant of Venice," the prominent and somewhat sensational reference to the "extreame cueltie of Shylocke the Jewe towards the sayd Merchant" might have led some to believe that the play was more about "Shylocke" than about the unnamed "Merchant."