William John Paul Gallagher (born 21 September 1972) is an English singer and songwriter who achieved fame as the lead vocalist of the rock band Oasis from 1991 to 2009. He later fronted the rock band Beady Eye from 2009 to 2014, before starting a successful solo career in 2017. Oasis had various line-up changes; Gallagher and his older brother Noel were the only constant members. One of the most recognisable figures in British rock music, Gallagher is noted for his distinctive vocal style and outspoken personality.

Gallagher was interested in joining a band called the Rain. After mutual agreement, the band underwent a name change to Oasis, and Noel was initially approached to be their manager. He was subsequently extended an invitation to join the band as their lead guitarist, which he accepted. The band's debut album, Definitely Maybe (1994), was a critical and commercial success during the emergence of Britpop. 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; however, all of their subsequent albums topped the UK charts, and they continued to tour, playing gigs to 1,000,000+ people worldwide, but particularly in Europe, and South America. In August 2009, following Noel's departure from Oasis, Gallagher and the remaining band members would go on to form Beady Eye, with whom he released two studio albums before they disbanded in 2014.

In 2017, Gallagher began his solo career with the release of his debut solo album, As You Were (2017), which proved to be a critical and commercial success. It topped the UK Albums Chart and was the ninth fastest-selling debut album of the 2010s in the UK, with over 103,000 units sold in its first week. In 2018, the album was certified platinum with over 300,000 units sold in the UK. His second album, Why Me? Why Not, received mostly positive reviews and topped the UK charts upon its release in September 2019. This made it his tenth chart-topping album including eight with Oasis, and it also became the fastest-selling vinyl of 2019. In March 2010, he was voted the greatest frontman of all time in a reader poll by Q magazine. In 2019, he received the MTV Europe Music Award for "Rock Icon". Liam's third album, C'mon You Know, was released in 2022 and became his fourth solo album to debut at number one on the UK Albums Chart. In 2024, Gallagher collaborated with ex-Stone Roses musician John Squire on the studio album Liam Gallagher & John Squire, which was released on 1 March 2024.