The 48-year-old singer was speaking as he and brother Noel Gallagher announced the release of documentary film Oasis Knebworth 1996 in cinemas worldwide on 23 September.
Liam admitted: “Knebworth for me was the Woodstock of the Nineties. It was all about the music and the people. I can’t remember much about it, but I’ll never forget it. It was biblical.”
He compared the Brit Pop band's concert in the ground of the stately home in Hertfordshire to the 1960s US music festival - widely regarded as a pivotal event in popular music culture.
Brother Noel, 54, joked: "I can’t believe we never played Rock ’n’ Roll Star.”
Among the Oasis hits that did feature during the live performance were Wonderwall, Live Forever, Don’t Look Back In Anger, Champagne Supernova and an orchestra-backed cover of Beatles track I Am The Walrus.
The band filmed backstage footage at the time - which has now been made into a feature length behind-the-scenes documentary as the band look back on their performance in front of the 250,000-strong crowd 25 years ago.
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Though Liam and Noel are not believed to have spoken to one another since an argument at a festival in Paris in August 2009 they both serve as executive producers on the film.
The documentary is directed by Grammy-award winning music video creator Jake Scott, son of Hollywood director Ridley Scott.
Noel previously revealed: "We were going to do the film of it then. But if you remember the timescale, we left Knebworth, went to America and that tour imploded . . . it all went t**s up.”
They performed at Knebworth in 1996 with drummer Alan White, Paul "Bonehead" Arthurs on rhythm guitar and Paul "Guigsy" McGuigan on bass.
The film's announcement may be bittersweet for fans - who were hoping the warring brother's would put aside their differences and mark the show's 25th anniversary with an Oasis reunion concert.
Oasis formed in Manchester in 1991 and split following the brother's fight in 2009.
Both went on to have successful solo careers since going their separate ways. Liam as the lead singer of Beady Eye and Noel with the band High Flying Birds.
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