"Spider" John Koerner (August 31, 1938 – May 18, 2024) was an American guitarist, singer, and songwriter. He was best known as a guitarist and vocalist in the blues trio Koerner, Ray & Glover, with Dave Ray and Tony Glover. He also made albums as a solo performer and with Willie Murphy, and was an important mentor to the young Bob Dylan.

In a profile of Koerner for the magazine fRoots in 2010, Ian Anderson wrote that "Spider John Koerner is an American national treasure, a genuine folk blues hero. Bizarrely, most of his fellow countrypersons remain blissfully unaware of this, in spite of his being one of the key figures of the 1960s folk boom." The Encyclopedia of Popular Music called him "one of the most talented songwriters of his generation."