  Since their proposal nearly half a century ago, physicists have sought axions
in both high energy and condensed matter settings. Despite intense and growing
efforts, to date experimental success has been limited, with the most prominent
results arising in the context of topological insulators. Here we propose a
novel mechanism whereby axions can be realized in quantum spin liquids. We
discuss the necessary symmetry requirements and identify possible experimental
realizations in candidate pyrochlore materials. In this context, the axions
couple both to the external and to the emergent electromagnetic fields. We show
that the interaction between the axion and the emergent photon leads to a
characteristic dynamical response, which can be measured experimentally in
inelastic neutron scattering. This work sets the stage for studying axion
electrodynamics in the highly tunable setting of frustrated magnets.
