Jack Lancaster is a British composer, record producer and musician.

In the late 1960s, Lancaster co-founded the British rock group Blodwyn Pig with Jethro Tull guitarist Mick Abrahams and in the late 1970s he was a member of the British progressive rock group Aviator with former Jethro Tull drummer Clive Bunker, former Manfred Mann's Earth Band guitarist Mick Rogers, and former Caravan and Quantum Jump bassist John G. Perry that released two albums on the EMI America Records label (Lancaster appeared only on the band's debut). In between these high-profile projects, Lancaster collaborated with keyboardist Robin Lumley in the studio band The Soul Searchers with a line-up that included guitarists Gary Moore and John Goodsall, bassist Percy Jones, and drummer Bill Bruford. This group released one 7" single Scaramouche b/w Head Stand in 1975 for EMI Records.

Lancaster performed on two Jazz Fusion records with Lumley that were released by RSO Records in the mid-1970s. The first was The Rock Peter and the Wolf (1975), a rock version of Russian composer Sergei Prokofiev's Peter and the Wolf, and the second was Marscape (1976); both albums featured the contributions of members of what would become Lumley's future band Brand X (John Goodsall, Percy Jones, and Phil Collins on drums).

In 1979, Lancaster and Dutch keyboardist Rick van der Linden released the electronic album Wild Connections on the Acrobat Records label that featured former Blue Mink drummer Barry Morgan and The English Chorale. 1980, Lancaster released a solo album on the Kamera Records label titled Skinningrove Bay that included Rod Argent, Clive Bunker, Phil Collins, Robin Lumley, Gary Moore, John G. Perry, Mick Rogers, Rick van der Linden and Bernie Frost.

Since then he has performed live on tour, composed for television and film, performed as a session musician and has produced, written and arranged recording sessions with artists including Gary Moore, Phil Collins, Rod Argent, Anthony Phillips, Hans Zimmer, Stéphane Grappelli, Brian Eno, The View, Vangelis and Rick van der Linden. Lancaster lives in Hollywood.