John Lennon
From Art Rock Wiki
As one of the two main songwriters of The Beatles, John Lennon was instrumental in the creation of Art Rock, particularly the genres of Art Rock proper and Avant Rock.
Lennon began his solo career while still in the Beatles and his early collaborations with Yoko Ono resulted in his most avant garde music. However he soon pulled back and his solo career is mostly not "art rock" in any meaningful sense.