Gallagher began playing guitar at the age of 13, and became a roadie and technician for Inspiral Carpets at the age of 21. He learned that his brother Liam had formed a band called The Rain, which eventually became Oasis, and Liam invited him to join them as the lead guitarist. He agreed on condition that he would write their material. The band's debut album, Definitely Maybe (1994), was a critical and commercial success. Their second album, (What's the Story) Morning Glory? (1995), reached the top of the album charts in many countries, and their third studio album, Be Here Now (1997), became the fastest-selling album in UK chart history. Britpop eventually declined in popularity and Oasis failed to revive it, though their final two albums, Don't Believe the Truth (2005) and Dig Out Your Soul (2008), were hailed as their best efforts in over a decade. In August 2009, following an altercation with Liam, Noel announced his departure from Oasis. Gallagher would go on to form Noel Gallagher's High Flying Birds, with whom he has released three studio albums.

Oasis' time was marked by turbulence, especially during the peak of Britpop, during which Noel was involved in several disputes with Liam and their fights and wild lifestyles regularly made tabloid headlines. The band notably had a rivalry with fellow Britpop band Blur. Noel himself was often regarded as the spearhead of the Britpop movement, with NME deeming several Britpop bands (including Kula Shaker, Ocean Colour Scene, and Cast) "Noelrock". Many have praised his songwriting, with Beatles producer George Martin calling him "the finest songwriter of his generation". Conversely, he was voted the most overrated guitarist of the last millennium in a 1999 poll, and the ninth most overrated ever in a 2002 listener survey. He cited the former as the award he most enjoyed receiving. Gallagher holds both British and Irish citizenship.