Brand New is an American rock band formed in 2000 from Long Island, New York. Consisting of lead vocalist and rhythm guitarist Jesse Lacey, lead guitarist Vincent Accardi, bassist Garrett Tierney and drummer Brian Lane, the band earned critical recognition as one of the most influential emo bands, and was acclaimed for their musical development and artistic innovation compared to other groups in the scene from which they originated.

In the 1990s, Lacey, Tierney and Lane played in the Levittown band the Rookie Lot, and Brand New was formed with Accardi after Lacey left his position as the founding bassist for Taking Back Sunday. The band signed to Triple Crown Records and released a pop-punk debut album Your Favorite Weapon. The band began to incorporate indie rock influences on their second album Deja Entendu, released in 2003 to positive reviews over the band's stylistic changes. Its two singles "The Quiet Things That No One Ever Knows" and "Sic Transit Gloria... Glory Fades" both entered the top 40 on the UK Singles Chart. Deja Entendu was eventually certified Gold in the US.

The demos for the band's major label debut on Interscope Records were leaked onto the internet in 2006. After reworking the material, the band released The Devil and God Are Raging Inside Me, which earned retrospective critical acclaim for its influence on emo. It was also certified Gold in the US, and the single "Jesus Christ" peaked at number 30 on Billboard's Alternative Songs chart. Accardi's role as a lyricist increased on the band's fourth album Daisy (2009), which debuted at number six on the Billboard 200 and featured a more post-hardcore and noise rock sound.

While Brand New toured consistently and played several prominent festivals, the band went six years without releasing music before the singles "Mene" (2015) and "I Am a Nightmare" (2016) surfaced. Brand New's fifth and most recent album, Science Fiction, was surprise-released in August 2017 through the band's own record label, Procrastinate! Music Traitors. It debuted at number-one on the Billboard 200, receiving both critical acclaim and commercial success. The band repeatedly announced plans to break up in 2018, but remained inactive for seven years without an official announcement of a breakup in the wake of 2017 sexual misconduct allegations against Lacey. The band reunited in 2024 for a charity show, followed by a US and UK tour in 2025.

In the late 1990s, Jesse Lacey, Garrett Tierney and Brian Lane were all members of the Levittown, New York post-hardcore band the Rookie Lot, along with Brandon Reilly and Alex Dunne of Crime in Stereo. The Rookie Lot split and did not play for a while until Lacey, Lane and Tierney started to rehearse again. After Reilly joined The Movielife, they recruited guitarist Vincent Accardi from the band One Last Goodbye. The quartet all lived within ten minutes of each other.

All four members had backgrounds linking into their local Long Island independent and hardcore music scenes, but with influences ranging from Buddy Rich to Archers of Loaf. Brand New was officially formed in 2000 in a basement in Merrick, New York. Their initial intention was always to "move outside of whatever notions they felt inclined to when they were making music as younger people." The band gained exposure in the local scene through playing shows with alternative rock contemporaries Midtown and post-hardcore bands like Glassjaw, while also self-releasing a four-song demo. The band's first show was at the Garden City bowling alley as the opener for Long Island hardcore band Silent Majority.

Brand New signed to Triple Crown Records just after their second-ever show. The band had released a demo for Warner Bros. Records, but the label did not believe that the band had a hit single in their catalog that was worth signing them for. In response, Lacey immediately wrote "Last Chance to Lose Your Keys" at the label office to serve as their single, but Warner Bros. declined to make an offer and Brand New ended up with Triple Crown instead.

Lane and Reilly came up with the band name Brand New, which Lacey said was "somewhat in jest because nothing about the band is really that new... we weren't trying to break ground with a new kind of sound or anything." Later, Lacey said that interpretation was not his original intention, claiming that "a friend of ours said he would call his band Brand New but he never got a new band so we took it. I wish it were something as clever as a sarcastic take on the state of music."