  This chapter summarizes our current understanding of the ionosphere of
Saturn. We give an overview of Saturn ionospheric science from the Voyager era
to the present, with a focus on the wealth of new data and discoveries enabled
by Cassini, including a massive increase in the number of electron density
altitude profiles. We discuss recent ground-based detection of the effect of
"ring rain" on Saturn's ionosphere, and present possible model interpretations
of the observations. Finally, we outline current model-data discrepancies and
indicate how future observations can help in advancing our understanding of the
various controlling physical and chemical processes.
