The second season of Seinfeld, an American television series created by Jerry Seinfeld and Larry David, began airing on January 23, 1991, on NBC.

Because of the commencement of the first Gulf War, the second season's premiere was postponed one week. The season comprised 12 episodes, and concluded its initial airing on June 26, 1991. It introduced a number of characters who played significant roles in later episodes, such as Jerry's Uncle Leo and Jerry's neighbor Newman.

Filming of the show moved from Hollywood to Studio City, Los Angeles. One episode, "The Bet", remained unfilmed, as it was considered too provocative by the network, as well as several cast and crew members. Two new writers joined the writing staff, Larry Charles and Peter Mehlman, who would continue to write for the show in later seasons. Even though season two started out with poor ratings, bringing the season to a two-month hiatus, the rest of the season was positively received by critics and was nominated for three Primetime Emmy Awards.

A Seasons 1 and 2 DVD box set was released by Sony Pictures Home Entertainment in the United States and Canada on November 23, 2004, 13 years after it completed broadcast on television. In addition to every episode from the two seasons, the DVD release features an episode from the third season that was held over, bonus material, including deleted scenes, inside looks, bloopers, and commentaries. Four million copies of the DVD were sold by the end of the year, making it one of the best-selling DVDs of all time.

The show features an ensemble cast of four characters: Jerry Seinfeld stars as a fictional version of himself; Jason Alexander portrays Seinfeld's neurotic friend George Costanza; Julia Louis-Dreyfus plays Elaine Benes, Seinfeld's ex-girlfriend; and Michael Richards stars as Seinfeld's neighbor Kramer. Matthew Gilbert of The Boston Globe noted the characters' evolution during the season: "As the seasons progress, you can see Michael Richards turn Kramer [...] from a vague eccentric [...] into a stylized creation who redefined TV's quirky-neighbor type with Danny Kaye accents. You can see Julia Louis-Dreyfus [...] develop Elaine from a puffy-haired gal pal (who wasn't in the pilot) into a delightfully petty urbanite. And you can see Jason Alexander push George from 'a blatant Woody Allen impression', as the actor acknowledges, into a more offensive and hyperactive neurotic."

The season introduced several characters who returned later on the show. The episode "The Pony Remark" featured the second appearance of Helen and Morty Seinfeld, both of whom had previously appeared in the season 1 episode "The Stake Out". In "The Stake Out", Morty was portrayed by Phil Bruns; however, David and Seinfeld wanted the character to be harsher, and re-cast him with Barney Martin, who auditioned for the part on October 15, 1990, at 12:45 pm. Martin was unaware that another actor had already established the part. Helen was portrayed by Liz Sheridan, who had played her in "The Stake Out". The same episode introduced Jerry's uncle Leo, portrayed by Len Lesser, who was known for his acting in gangster films such as The Outlaw Josey Wales and Kelly's Heroes. When Lesser auditioned for the part on October 22, 1990, he incited laughs from David, Seinfeld, and casting director Marc Hirschfeld, but did not understand why, because he did not think his lines were funny. Herschfield stated that when Lesser had auditioned it was clear that he was the right actor for the part. "The Revenge" features the first appearance by Newman (voiced by David), a suicidal man who lives in Jerry's apartment building. In "The Revenge", Newman remained out of sight, although he appeared in a deleted scene. Before this scene was cut, William Thomas, Jr. had been cast for the part. Although the writing staff never intended for Newman to return to the show, the idea of having Wayne Knight as a neighbor appealed to them. Therefore, Knight was re-cast in the role of Newman for the season 3 episode "The Suicide".

Seinfeld was produced by Castle Rock Entertainment, and in the United States, it aired on NBC. The producers of the show were Larry David, George Shapiro and Howard West. Tom Cherones directed all episodes of the season. Series co-creators David and Jerry Seinfeld wrote eight of the season's episodes. The writing staff was joined by Larry Charles, who wrote three episodes, and Peter Mehlman, who wrote "The Apartment".

Starting with the season premiere, filming of the show moved from Desilu Cahuenga, in Hollywood, California, to CBS Studio Center, in Studio City, Los Angeles, California. Tom Azzari worked as set designer during season two; he often re-used sets from the first season, because Castle Rock Entertainment had rented a large storage facility in which sets were stored, to save money. Although the scenes in Monk's Cafe were filmed at CBS Studio Center, the exterior of Tom's Restaurant, a diner at the intersection of Broadway and 112th Street in Manhattan, was used as the exterior for the cafe. The second season of Seinfeld was supposed to start airing on January 16, 1991, but the premiere was postponed one week because of the commencement of the first Gulf War.