Oasis is an English rock band formed in Manchester in 1991. The group initially consisted of Liam Gallagher (lead vocals), Paul "Bonehead" Arthurs (guitar), Paul "Guigsy" McGuigan (bass guitar) and Tony McCarroll (drums), with Liam asking his older brother Noel Gallagher (lead guitar, vocals) to join as a fifth member a few months later to finalise their formation. Noel became the de facto leader of the group and took over the songwriting duties for the band's first four albums. They are regarded as one of the defining and most globally successful groups of the Britpop genre.

Oasis signed to independent record label Creation Records in 1993 and released their record-setting debut album Definitely Maybe (1994), which topped the UK Albums Chart and quickly became the fastest-selling debut album in British history at the time. The following year, they released (What's the Story) Morning Glory? (1995) with new drummer Alan White in the midst of a highly publicised chart rivalry with peers Blur, dubbed by the British media as the "Battle of Britpop". Spending ten weeks at number one on the British charts, (What's the Story) Morning Glory? was also an international chart success and became one of the best-selling albums of all time, the fifth-best-selling album in the UK and the best-selling album in the UK of the 1990s. The Gallagher brothers featured regularly in tabloid newspapers throughout the 1990s for their public disputes and wild lifestyles. In 1996, Oasis performed two nights at Knebworth for an audience of 125,000 each time, the largest outdoor concerts in UK history at the time. In 1997, Oasis released their highly anticipated third studio album, Be Here Now, which became the fastest-selling album in UK chart history but retrospectively was seen as a critical disappointment.

Founding members Arthurs and McGuigan left in 1999 during the recording of the band's fourth studio album Standing on the Shoulder of Giants (2000). They were replaced by former Heavy Stereo guitarist Gem Archer on guitar and former Ride guitarist Andy Bell on bass guitar. White departed in 2004, replaced by guest drummer Zak Starkey, and later by Chris Sharrock. Oasis released three more studio albums in the 2000s: Heathen Chemistry (2002), Don't Believe the Truth (2005) and Dig Out Your Soul (2008). The group abruptly disbanded in 2009 after the sudden departure of Noel Gallagher. The remaining members of the band continued under the name Beady Eye until their disbandment in 2014. Both Gallagher brothers have since had successful solo careers. In 2024, Oasis announced that they would reform in 2025 for worldwide performances as part of the Oasis Live '25 Tour.

As of 2024, Oasis have sold over 75 million records worldwide, making them one of the best-selling music artists of all time. They are among the most successful acts in the history of the UK singles chart and the UK Albums Chart, with eight UK number-one singles and eight UK number-one albums. The band also achieved three Recording Industry Association of America (RIAA)-certified Platinum albums in the US. They won 17 NME Awards, nine Q Awards, four MTV Europe Music Awards and six Brit Awards, including one in 2007 for Outstanding Contribution to Music and one for the "Best Album of the Last 30 Years" for (What's the Story) Morning Glory?. They were also nominated for two Grammy Awards.