John Klemmer (born July 3, 1946) is an American saxophonist, composer, song writer and arranger.
He was born in Chicago, Illinois, and began playing guitar at the age of 5 and alto saxophone at the age of 11. His other early interests included graphics and visual art, writing, dance, puppetry, painting, sculpting and poetry. He studied at schools that include The Art Institute of Chicago and began touring with various local midwest "ghost big bands" (Les Elgart, Woody Herman) as well as playing with small local jazz and rock groups. After switching to tenor saxophone in high school, Klemmer participated actively in the local Chicago jazz scene, playing with commercial small groups and big bands while leading his own groups in the Chicago area and touring.