Weezer is an American rock band formed in Los Angeles, California, in 1992. Since 2001, the band has consisted of Rivers Cuomo (lead vocals, guitar, keyboards), Patrick Wilson (drums), Brian Bell (guitar, keyboards, backing vocals), and Scott Shriner (bass, keyboards, backing vocals). They have sold 10 million albums in the United States and over 35 million worldwide.

After signing to Geffen Records in 1993, Weezer released their acclaimed self-titled debut album, also known as the Blue Album, in May 1994. Backed by music videos for the singles "Undone – The Sweater Song", "Buddy Holly", and "Say It Ain't So", the Blue Album became a multi-platinum success. Weezer's second album, Pinkerton (1996), featuring a darker, more abrasive sound, was a commercial failure and initially received mixed reviews, but achieved cult status and acclaim later. Both the Blue Album and Pinkerton have been cited among the best albums of the 1990s. Following the tour for Pinkerton, the founding bassist, Matt Sharp, left the band and Weezer went on hiatus.

In 2001, Weezer returned with the Green Album with their new bassist, Mikey Welsh. With a more pop-oriented sound, and promoted by singles "Hash Pipe" and "Island in the Sun", it was a commercial success and received mostly positive reviews. After the Green Album tour, Welsh left for health reasons and was replaced by Scott Shriner. Weezer's fourth album, Maladroit (2002), incorporated a hard rock sound and achieved mostly positive reviews, but weaker sales. Make Believe (2005) received mixed reviews; however, its single "Beverly Hills" became Weezer's first single to top the US Modern Rock Tracks chart and their first to reach the top ten on the Billboard Hot 100.

In 2008, Weezer released the Red Album. Its lead single, "Pork and Beans", became the third Weezer song to top the Modern Rock Tracks chart, backed by a Grammy-winning music video. Raditude (2009) and Hurley (2010) both featured more modern pop production, along with songs written with other artists, receiving further mixed reviews and moderate sales. Everything Will Be Alright in the End (2014) and the White Album (2016) returned to a rock style that was reminiscent of their 1990s sound, mixed with modern alternative production, and achieved more positive reviews, while Pacific Daydream (2017) returned to a more mainstream pop sound. In 2019, Weezer surprise-released an album of covers, the Teal Album, followed by the Black Album. In 2021, they released OK Human, which featured an orchestral pop sound and received acclaim, followed by the hard rock-inspired Van Weezer. In 2022, Weezer released SZNZ, a series of four albums based on the four seasons. Their upcoming twentieth album, the Gold Album, is due in 2026.

Lead vocalist and guitarist Rivers Cuomo moved to Los Angeles from Connecticut, in 1989 with his high school metal band, Avant Garde, which was later renamed Zoom. After the group disbanded, Cuomo met drummer Patrick Wilson and moved in with him and Wilson's friend Matt Sharp. Cuomo moved away from metal and explored alternative rock influences such as Nirvana, Pixies and Sonic Youth. He and Wilson formed a band, Fuzz, and enlisted Scottie Chapman on bass. Chapman quit after a few early shows; the band reformed as Sixty Wrong Sausages, with Cuomo's friend Pat Finn on bass and Jason Cropper on guitar, but soon disbanded. Cuomo moved to Santa Monica, California, and recorded dozens of demos, including the future Weezer songs "The World Has Turned and Left Me Here" and "Undone – The Sweater Song". Sharp was enthusiastic about the demos, and became the group's bassist and de facto manager.

Cuomo, Wilson, Sharp, and Cropper formed Weezer on February 15, 1992. Their first show was on March 19, 1992, closing for Keanu Reeves' band Dogstar. They took their name from a nickname Cuomo's father gave him, which was based on a character called "Wheezer" from the Our Gang short films. Cuomo gave Sharp one year to get the band a record deal before Cuomo accepted a scholarship at the University of California, Berkeley. In 1992, Weezer recorded a demo, The Kitchen Tape, including a version of the future Weezer single "Say It Ain't So". The demo was heard by Todd Sullivan, an A&R man at Geffen Records, who signed Weezer in June 1993.

Weezer recorded their debut album with the musician and producer Ric Ocasek at Electric Lady Studios in New York City. Cropper was fired during recording, as Cuomo and Sharp felt he was threatening the band chemistry. He was replaced by Brian Bell. Weezer's self-titled debut album, also known as the "Blue Album", was released in May 1994. Described by Pitchfork as integrating "geeky humor, dense cultural references, and positively gargantuan hooks", it combined alternative rock, power pop, polished production and what AllMusic critic Stephen Thomas Erlewine called an "'70s trash-rock predilection ... resulting in something quite distinctive".

Weezer's first single, "Undone – The Sweater Song", was backed by a music video directed by Spike Jonze; filmed in an unbroken take, it featured Weezer performing on a sound stage with little action, barring a pack of dogs swarming the set. The video became an instant hit on MTV. The song reached No. 57 on the Billboard Hot 100. Jonze also directed Weezer's second video, "Buddy Holly", splicing the band into footage from the 1970s television sitcom Happy Days. The video achieved heavy rotation on MTV and won four MTV Video Music Awards, including Breakthrough Video and Best Alternative Music Video. "Buddy Holly" peaked at No. 18 on the Hot 100 Airplay and No. 2 on the Billboard Modern Rock chart. The song is included on Rolling Stone's 500 Best Songs Of All Time. A third single, "Say It Ain't So", followed. It was met with critical acclaim and later Pitchfork ranked it No. 10 on the top 200 tracks of the 90s list. The song reached No. 51 on the Hot 100 Airplay chart and No. 7 on the Billboard Modern Rock chart. Additionally, the track was included in Rolling Stone's list of "The Top 100 Guitar Songs of All Time".