  Scaling relations of galaxy clusters are a powerful probe of cosmic isotropy
in the late Universe. Owing to their strong cosmological dependence, galaxy
cluster scaling relations can obtain tight constraints on the spatial variation
of cosmological parameters, such as the Hubble constant ($H_0$), and detect
large-scale bulk flow motions. Such tests are crucial to scrutinise the
validity of $\Lambda$CDM in the local Universe and determine at what cosmic
scales (if any) extra-galactic objects converge to isotropy within the Cosmic
Microwave Background rest frame. This review describes the methodology for
conducting cosmic isotropy tests with cluster scaling relations and examines
possible systematic biases. We also discuss the results of past studies that
reported statistically significant observed anisotropies in the local Universe.
Finally, we explore the future potential of cluster scaling relations as a
cosmic isotropy probe given the large amount of multi-wavelength cluster data
expected in the near future.
