Iain David McGeachy (11 September 1948 – 29 January 2009), known professionally as John Martyn, was a British guitarist and singer-songwriter. Over a 40-year career, he released 23 studio albums, and received frequent critical acclaim. The Times described him as "an electrifying guitarist and singer whose music blurred the boundaries between folk, jazz, rock and blues".

Martyn began his career at age 17 as a key member of the Scottish folk music scene, drawing inspiration from American blues and English traditional music, and signed with Island Records. By the 1970s he had begun incorporating jazz and rock into his sound on albums such as Solid Air (1973) and One World (1977), as well as experimenting with guitar effects and tape delay machines such as Echoplex. Domestic and substance abuse problems marked his personal life throughout the 1970s and 1980s, though he continued to release albums while collaborating with figures such as Phil Collins and Maeve Aubele, Carolyn Woolham and Lee "Scratch" Perry. He remained active until his death in 2009.