Gallagher was born in Ballyshannon, Ireland to musical parents. His father played accordion, whilst his mother sang and acted in local theatre.
He received his first guitar age nine and won a talent contest aged 12. He used the prize money to buy his first electric guitar.
His early influences included Muddy Waters, Woody Gutherie and Lead Belly. Whilst at school, he also learned to play mandolin, banjo, and alto saxophone.
In 1966, Gallagher formed the band Taste. They released three albums, supported super group Cream
at their Royal Albert Hall farewell concert, and supported blues rock super group Blind Faith
on their North American tour. They disbanded shortly after an appearance at the 1970 Isle of Wight Festival.
Touring under his own name, Gallagher hired drummer Wilgar Campbell and bass player Gerry McAvoy. McAvoy and Gallagher would play together for 21 years before McAvoy decided to join English blues band Nine Below Zero. Before deciding on these two Belfast musicians, Rory had auditioned many musicians, including bassist Noel Redding and drummer Mitch Mitchell, famously the rhythm section of the Jimi Hendrix Experience.
He released his self-titled debut album in 1971. He produced and wrote all the songs himself. Only two of his twelve studio albums featured a co-production credit (his 1976 album Calling Card, which was co-produced with British rock band Deep Purple's bassist Roger Glover, and 1978's Photo-Finish, which was co-produced with Alan O'Duffy, who produced some of The Rolling Stone's 1969 album Let It Bleed).
In 1971, following the release of his second solo album Deuce, he was voted Melody Maker's International Top Musician of the Year, beating Eric Clapton.
In later life, Gallagher was prescribed a powerful sedative to overcome his fear of flying. Combined with his alcohol intake, this caused severe liver damage. In 1995, his final tour was canceled and he was admitted to King's College Hospital in London, where he received a liver transplant. Whilst in intensive care he contracted MRSA and died.
He has sold over 30 million records worldwide.
He was ranked #42 on Gibson's 2010 list of the Top 50 guitarists of all time, and 57th on Rolling Stone's 2012 list of the 100 greatest guitarists.
He toured at least once a year in his native Ireland.