  Galaxy clusters contain large magnetic fields that make them excellent
targets to search for ultralight Axion-Like Particles (ALPs). ALP-photon
interconversion imprints quasi-sinusoidal oscillations on the X-ray spectra of
point sources in or behind the cluster. The absence of substantial oscillations
allows us to place bounds on $g_{a \gamma \gamma}$. Here the bounds from the
{\it Chandra} X-ray observations of NGC1275 are presented, as well as those
predicted for the {\it Athena} X-ray observatory, due to launch in 2028.
