ESA/Hubble is pleased to announce the release of the Hubble Catalog of Variables (HCV), the first full, homogeneous catalogue of variable sources based on archival HST data. The HCV was developed over four years by a team of astronomers at the National Observatory of Athens, led by Alceste Bonanos and sponsored by ESA in collaboration with STScI. The HCV is the deepest catalogue of variables available. In total, the HCV includes 84 428 candidate variable sources (out of 3.7 million HSC sources that were searched for variability) with V ≤ 27 mag; for 11 115 of them the variability is detected in more than one filter. The data points in a light curve range from 5 to 120, the time baseline ranges from under a day to over 15 years, and ∼ 8% of variables have amplitudes in excess of 1 mag. The HCV is expected to become a key resource for the community, as it includes variable stars in the Milky Way and nearby galaxies, as well as transients and variable AGN, including low-luminosity AGN. The HCV contains many interesting high-amplitude variables, which require further study.