Jazz emerged in the twentieth century as one of the great African-American contributions to world culture. Within philosophical theorising about music, jazz has often functioned – sometimes explicitly, sometimes implicitly – as an ‘exotic’ alternative to Western classical music, which has functioned as the de facto paradigm of musical activity in the field. The result has been a focus on one central aspect of jazz practice for much of its history that was largely moribund in the classical tradition throughout the twentieth century, namely improvisation in instrumental jazz performances. Philosophers have addressed the nature of improvisation and its implications for the ontology and values of jazz – its musical values as well as its ethical and political implications. It is this work that I provide an overview of here. (For some philosophical reflections on jazz song, see Brown 2013; Carvalho 2013; Levinson 2013a and 2013b; and Bicknell 2015, pp. 41–70.)