John Kirby (born John Kirk on December 31, 1908, in Winchester, Virginia, and died June 14, 1952, in Hollywood, California) was an influential American jazz double-bassist and bandleader. Raised by Reverend Washington Johnson and his wife Nancy after being given up for adoption, Kirby developed an early interest in music, taking piano and valve trombone lessons. His formal education ended around 1923, and he married Mary Moten in 1925, with whom he had a daughter, Yvonne Constance Kirk.

Kirby's career in music began in earnest when he moved to Baltimore in 1928, where he met key figures like trombonist Jimmy Harrison and saxophonist Coleman Hawkins. Initially a trombonist, he switched to tuba and later to double bass, studying under renowned bassists Pops Foster and Wellman Braud. By 1936, Kirby had established himself as a successful sideman in the New York City jazz scene, working with notable bands including Fletcher Henderson's orchestra.

In the late 1930s and early 1940s, Kirby led a chamber jazz sextet that became known for its sophisticated arrangements and classical influences, producing hits such as "Loch Lomond" and "Undecided." His band, often referred to as the Onyx Club Boys, was a staple of the Swing era, known for its unique sound and complex arrangements.

Kirby was a pioneer in the chamber jazz genre, and although he was not a major soloist like Jimmie Blanton, his vision for a cool-toned, three-horn sextet that could effortlessly blend classical music with jazz standards left a lasting impact on the jazz world.