The International Organ Festival (IOF) is a biennial music festival and organ competition held in St Albans, England since 1963. Originally held annually, it was changed to every two years in 1965 due to the complexity of organising the increasingly ambitious programme. The festival is run mainly by volunteers.
The festival was conceived by Peter Hurford to celebrate the building of the new organ in St Albans Cathedral by Harrison & Harrison. The main competitions are still conducted on this instrument, its eclectic style and modern electropneumatic action now complemented by another self-contained tracker action instrument which The International Organ Festival Society, the charity which runs the Festival, has had built for its own use and sited at St Saviour's Church, St Albans. This was built by Peter Collins in the style of, and in homage to, the early 18th century German organ builder Andreas Silbermann. There is a new (2005) organ in St Peter's Church, St Albans by Mander Organs, which has played a role in the festival and competitions since 2007.
There are two main competitions, the interpretation competition and the improvisation competition (formerly known as the Tournemire Prize). Judges have included Piet Kee, Marie-Claire Alain, Anton Heiller, Ralph Downes, Thomas Trotter, Ton Koopman, Naji Hakim, Daniel Roth and David Sanger. The competition is considered prestigious, as may be judged by the list of past winners, and judges have occasionally decided not to award first prize.