Jerome "Jerry" Seinfeld (/ˈsaɪnfɛld/; SYNE-feld) is the title character and the main protagonist of the American television sitcom Seinfeld (1989–1998). The straight man among his group of friends, this fictionalized version of comedian Jerry Seinfeld was named after, co-created by, and played by Seinfeld himself. The series revolves around Jerry's misadventures with his best friend George Costanza, neighbor Cosmo Kramer, and ex-girlfriend Elaine Benes. He is usually the voice of reason amid his friends' antics and the focal point of the relationship.

In contrast to the series' supporting characters, he rarely runs into major personal problems. Jerry is the only main character on the show to maintain the same career (a stand-up comedian, like the real Seinfeld) throughout the series. He is the most observational character, sarcastically commenting on his friends' quirky habits. Much of the show's action takes place in Jerry's apartment located in New York City at 129 West 81st Street, apartment 5A (3A in seasons 1 and 2). He and his friends also frequently have coffee or meals together at Monk's Café.

Jerry appears in all 180 episodes of Seinfeld (including several two-part episodes), the only character in the show to do so.

In the show's setting, Jerry is the straight man, a figure who is "able to observe the chaos around him but not always be a part of it." Plot lines involving Jerry often concern his various relationships – Apparently afraid of commitment, Jerry often finds minor reasons to break up with women, such as her eating peas "one at a time".

Jerry is ex-boyfriend and still friend of Elaine Benes, who comments on this behavior as: “You know, every time I think I’m sure that you’re the shallowest man on earth, you find a way to drain another couple of inches out of the pool.” Elaine points out that he has "never felt remorse."

Jerry will often nonchalantly state, "That's a shame" when something bad happens. A recurring joke is Jerry behaving unchivalrously towards Elaine, such as not helping her carry groceries or heavy objects, ignoring her when she is upset, and taking a first class upgrade on a flight for himself, leaving Elaine in economy. Jerry, George and Elaine all share a general trait of not letting go of other characters' remarks and going to great lengths to be proven right. In one episode, Jerry rents a house in Tuscany, just because Elaine's boyfriend told him there were none available (though he never actually wanted to rent the house, but was only inquiring if he theoretically could rent one).

Despite his usual indifference to his friends and their actions, Jerry apparently is very satisfied with his life, and feels worried about anything that might threaten the group lifestyle. In "The Invitations", for example, Jerry admits that he feels depressed about George getting married, seeing as how George will eventually leave the group and Jerry will never see him again. Once Elaine tells him that she is also "getting out" of the group, Jerry becomes so worried about a near future of just him and Kramer that he unknowingly almost walks into a car while crossing the street. In "The Bizarro Jerry", Jerry also grows panicky about losing the group dynamic when Kramer becomes too busy with his job and Elaine temporarily leaves to join the Bizarro group, claiming that "The whole system's breaking down!" In a deleted scene from the episode "The Letter", he claims that his friends are "not more important" than his girlfriends, but "they're as important."

Unlike George and Elaine, Jerry rarely runs into major personal problems. In "The Opposite", this tendency is explicitly pointed out, as Jerry goes through a number of experiences after which he invariably "breaks even", while his friends are going through intense periods of success or failure. In "The Rye", during a particularly trying time for Elaine, she angrily tells Jerry, "You know, one of these days, something terrible is going to happen to you. It has to!" Jerry simply replies, "No, I'm going to be just fine." Many of the problems he does run into are the result of the actions of his nemesis Newman, a postal worker. In the series finale, Jerry's streak of getting away with things is broken when he, and the rest of the group, are arrested for their indifference toward a mugging victim and sentenced to jail after multiple witnesses testify to their poor character.