Karl Edmond De Vere Wallinger (19 October 1957 – 10 March 2024) was a Welsh musician, songwriter and record producer. He was best known for leading the band World Party and for his mid-1980s membership of the Waterboys (contributing in particular to the arrangement and recording of their hit single "The Whole of the Moon").

Wallinger's songwriting credits include the World Party songs "Ship of Fools", which was a Top 40 hit in the United States, "Way Down Now", which reached number one on the Billboard Modern Rock chart, and "She's the One", which was later covered by Robbie Williams and became a hit single.

Wallinger was a multi-instrumentalist, which enabled him to demo and record the bulk of World Party material as a one-man band. Although he was right-handed, he played a right-handed guitar upside-down and left-handed.

Wallinger was born on 19 October 1957, in Prestatyn, Wales, to Julian and Phyllis Wallinger, and was one of six children. His father was an architect. He showed musical promise from an early age, immersing himself in the music of the Beatles (notably studying Sgt. Peppers Lonely Hearts Club Band and attempting not only to sing the words but to vocally recreate all of the sounds on the record), the Beach Boys, Bob Dylan, the Kinks, Buddy Holly and the Motown label. This was followed by classical training in piano (from the age of nine) and oboe (from the age of ten). Having spent time at choir school at Eton College, his musical skills then won him a music scholarship to another public school, Charterhouse in Surrey.

Wallinger's musical career began in Prestatyn in 1977 as a keyboard player with Pax, before forming the short-lived band Quasimodo with Dave Sharp and Nigel Twist (who both went on to be in the Alarm). Having moved to London, he then had a job in music publishing working for Northern Songs. He played keyboards for Peter Straker and was featured on the album Changeling, on which he received a writing credit for the song "Believer". In the same period he became musical director of The Rocky Horror Show.

Answering a "guitarist wanted" advertisement for Mike Scott's band the Waterboys, Wallinger instead persuaded Scott that the band needed a keyboard player. Joining in 1983, Wallinger played in the live band touring the first Waterboys album and contributed to the second album, A Pagan Place.

Though Wallinger was initially hired to play piano and organ (and to sing occasional backing vocals), his multi-instrumental and production skills impressed Scott and ensured that he played a far greater role on the third Waterboys album, This Is the Sea, significantly contributing to the band's 'Big Music' sound. While Scott concentrated on Steve Reichian orchestrations of the songs using multitracked pianos and guitar, Wallinger fleshed out the material with a variety of synthesised orchestrations, synth bass and percussion instruments. Wallinger also wrote the original music for "Don't Bang the Drum" (the opening track for This Is the Sea). Wallinger was particularly key to the final form of the best-known Waterboys song, "The Whole of the Moon", having taken Scott's original voice/piano/guitar structure and introduced polyphonic synthesizer parts, synth bass, upbeat and off-beat cymbal accents (all of these influenced by Prince) and a final tumbling backing vocal (influenced by David Bowie), as well as bringing in drummer Chris Whitten.

Musical rivalry and desire for control over creative credit made the relationship between Scott and Wallinger increasingly difficult and fractious, and in subsequent years the two would occasionally bicker publicly about who was responsible for the success of the music they created together. However, in 2012, Scott would remember, more generously, that "Karl was always there for me. He was a great engineer, got great sounds, [and] was very patient while I would play nine different guitars. Reefers may have been involved, and some all-nights. We had a lot of laughs and philosophical discussions."This is The Sea producer Mick Glossop also spoke approvingly of Wallinger's contributions: "Karl's a very giving person. He gave a lot to the Waterboys, certainly."