  We introduce well-separated $^{87}$Rb$^+$ ions into an atomic ensemble by
microwave ionization of Rydberg excitations and realize single-shot imaging of
the individual ions with an exposure time of 1 $\mu$s. This imaging sensitivity
is reached by using homodyne detection of ion-Rydberg-atom interaction induced
absorption. We obtain an ion detection fidelity of (80 $\pm$ 5)\% from
analyzing the absorption spots in acquired single-shot images. These \textit{in
situ} images provide a direct visualization of the ion-Rydberg interaction
blockade and reveal clear spatial correlations between Rydberg excitations. The
capability of imaging individual ions in a single shot is of interest for
investigating collisional dynamics in hybrid ion-atom systems and for exploring
ions as a probe for measurements of quantum gases.
