  The imaging of individual Ba$^{2+}$ ions in high pressure xenon gas is one
possible way to attain background-free sensitivity to neutrinoless double beta
decay and hence establish the Majorana nature of the neutrino. In this paper we
demonstrate selective single Ba$^{2+}$ ion imaging inside a high-pressure xenon
gas environment. Ba$^{2+}$ ions chelated with molecular chemosensors are
resolved at the gas-solid interface using a diffraction-limited imaging system
with scan area of 1$\times$1~cm$^2$ located inside 10~bar of xenon gas. This
new form of microscopy represents an important enabling step in the development
of barium tagging for neutrinoless double beta decay searches in $^{136}$Xe, as
well as a new tool for studying the photophysics of fluorescent molecules and
chemosensors at the solid-gas interface.
