James Minter Knepper (November 22, 1927 – June 14, 2003) was an American jazz trombonist. In addition to his own recordings as leader, Knepper performed and recorded with Charlie Barnet, Woody Herman, Claude Thornhill, Stan Kenton, Benny Goodman, Gil Evans, Thad Jones & Mel Lewis, Toshiko Akiyoshi & Lew Tabackin, and, most famously, Charles Mingus in the late 1950s and early 1960s. Knepper died in 2003 of complications of Parkinson’s disease.

Knepper was born in Los Angeles, California. 

While he was playing Funny Girl, he became a member of the Thad Jones/Mel Lewis Orchestra, a big band formed by trumpeter Thad Jones and drummer Mel Lewis around 1965, which began the 40-year tradition of Monday night jazz shows at the Village Vanguard in NYC’s Greenwich Village. The band performed for twelve years in its original incarnation, but since the death of Lewis in 1990 it has been known as the Vanguard Jazz Orchestra. They have maintained a Monday-night residency at the Village Vanguard for four decades. Knepper again toured the USSR, this time with TJML, as well as Japan and Europe with them, and appeared with them at the Montreux Jazz Festival in 1974.

In 1969, he toured and recorded “You Never Know Who Your Friends Are”, with keyboardist Al Kooper, in the jazz period which followed his departure from Blood, Sweat & Tears. Jimmy appeared on this concert tour which included shows at the Philadelphia Spectrum, and in Atlanta, where he briefly met Janis Joplin.