  We introduce multiplexed atom-cavity quantum electrodynamics with an atomic
ensemble coupled to a single optical cavity mode. Multiple Raman dressing beams
establish cavity-coupled spin-wave excitations with distinctive spatial
profiles. Experimentally, we demonstrate the concept by observing spin-wave
vacuum Rabi splittings, selective superradiance, and interference in the
cavity-mediated interactions of two spin waves. We highlight that the current
experimental configuration allows rapid, interchangeable cavity-coupling to 4
profiles with an overlap parameter of less than 10%, enough to demonstrate, for
example, a quantum repeater network simulation in the cavity. With further
improvements to the optical multiplexing setup, we infer the ability to access
more than $10^3$ independent spin-wave profiles.
