John Sebastian (born John Sebastian Pugliese; April 25, 1914 − August 18, 1980) was an American musician and composer known as a master of the classical chromatic harmonica. He was the first harmonicist to adopt an all-classical repertoire and, along with Larry Adler and Tommy Reilly, established the harmonica as a serious instrument for classical music. In addition to performing, Sebastian increased the range of classical music available for the harmonica by transcribing numerous existing classical works for the harmonica, composing works of his own, and commissioning or otherwise encouraging other composers to write for the instrument.

He is the father of singer-songwriter John B. Sebastian, a founder of the popular 1960s folk rock band The Lovin' Spoonful.