Taking Back Sunday is an American rock band from Amityville, New York, formed by guitarist Eddie Reyes and bassist Jesse Lacey in late 1999. The band's current members are Adam Lazzara (lead vocals), John Nolan (lead guitar, keyboards, vocals) and Shaun Cooper (bass guitar), accompanied by Nathan Cogan (guitar) and Mitchell Register (drums) for their live performances. The band's former members include original singer Antonio Longo, Jesse Lacey, Eddie Reyes, drummer Mark O'Connell, bassist Matthew Rubano, and guitarist-vocalists Fred Mascherino and Matthew Fazzi.

Lacey quit Taking Back Sunday in 1999 and in 2000 formed the rock band Brand New, with whom Taking Back Sunday would become embroiled in a highly publicized feud. Lazzara joined prior to the release of the band's 2002 debut album Tell All Your Friends, while Nolan and Cooper left the band in 2003 to form Straylight Run before returning in 2010. The band's breakthrough album, 2006's Louder Now, featured the popular lead single "MakeDamnSure", sold over 900,000 copies, and peaked at No. 2 on the United States Billboard 200, surpassing the band's previous Billboard 200 peak in 2004 at No. 3 with Where You Want to Be. They released their eighth studio album, 152, in 2023.

Taking Back Sunday has been referred to as "one of the more visible groups of the early-2000s emo boom." The staff of Consequence ranked the band at number 38 on their list of "The 100 Best Pop Punk Bands" in 2019.

Guitarist Eddie Reyes, who had formed and played in the Movielife, Mind Over Matter and Inside, and guitarist Jesse Lacey of the Rookie Lot founded Taking Back Sunday in Amityville, New York, in November 1999. The band's name was taken from a song by Long Island band The Waiting Process. Lacey moved to bass with the addition of guitarist John Nolan. The group also included vocalist Antonio Longo of One True Thing, and drummer Steven DeJoseph. Lacey left the band after a personal incident with Nolan. Lacey formed Brand New a year later. Nolan contacted Adam Lazzara to fill in on bass, which resulted in Lazzara moving from North Carolina to New York. Lazzara had met the band when they played a show near his hometown in North Carolina.

DeJoseph was unable to tour extensively because of personal issues and was waiting until the band had another drummer before leaving the group. Mark O'Connell, a friend of Reyes, heard about the opening and joined the group. After recording Taking Back Sunday's self-titled EP, Longo left the band and eventually played with The Prizefighter and the Mirror. In December 2000, Lazzara switched from bass to lead vocals. He never thought he would become the group's singer: "I remember getting into [Reyes'] Windstar with that [EP] and just driving around singing those songs, just to make myself actually do it." O'Connell suggested that the group needed a bassist, and brought in Shaun Cooper. Lazzara spoke of his initial thoughts on Cooper's talent in an interview with AP magazine, saying with Cooper it was "the best bass playing I'd ever seen in my life. I was like, "Oh my God, people can do that?'" In February 2001, Taking Back Sunday released a five-track demo before touring for a year.

While performing as an unsigned band, they received contract offers from labels that ultimately amounted to nothing. These included Triple Crown Records, who was apprehensive as they had just signed Brand New, and Drive-Thru Records' offer resulted from co-owner Richard Reines having mistaken Nolan for Lacey. Eventually, a friend of the band shared a demo with Victory Records sales and A&R representative Angel Juarbe. Jurabe then sent a copy to Victory founder Tony Brummel, who asked to see a live performance. Within two weeks of seeing them live, a contract was written up, and the band signed to Victory in December 2001.

Although other labels expressed interest in Taking Back Sunday, Victory Records encouraged them to make an album. The band's debut effort was recorded over a period of two weeks in December 2001 at Big Blue Meenie Recording Studio in New Jersey with producer Sal Villanueva. Lazzara fell ill around Christmas, and the sessions were delayed one to two weeks; recording concluded in early January 2002, and ended up costing $10,000. The debut album's name was revealed in February to be Tell All Your Friends; prior to the release of their debut, a music video for "Great Romances of the 20th Century" was released on March 4, 2002. It was directed by Christian Winters, a friend of the band. Winters made the video before the group signed with Victory, and the record company enjoyed it. The song was distributed to radio stations on March 12, and the full album was released on March 25. A video for "Cute Without the 'E' (Cut from the Team)" followed on December 10, 2002, and "You're so Last Summer" on November 24, 2003, following a radio release the previous September. Both videos were also directed by Winters.

Lazzara was suffering from a drinking problem around this time and cheated on Nolan's sister, Michelle, who he had been dating for a while. After playing Skate & Surf Festival in late April 2003, Lazzara apologized to Nolan later that evening. However, Nolan later learned the apology had been insincere, and both Nolan and Cooper officially told the other three band members they were leaving the band two days later. Nolan publicly reasoned that his departure resulted from exhaustion from touring; Lazzara reiterated this reason, and revealed Cooper had left because he did not want to be in the band without Nolan. In truth, Nolan later revealed there was constant fighting within the group, with each member feeling they were not receiving enough credit for the group's success.