We present the Heraklion Extragalactic Catalogue, or HECATE, an all-sky value-added galaxy catalogue, aiming to facilitate present and future multiwavelength and multimessenger studies in the local Universe. It contains 204 733 galaxies up to a redshift of 0.047 (D <~ 200 Mpc) , and it is >50 per cent complete in terms of the B-band luminosity density at distances in the 0-170 Mpc range. By incorporating and homogenizing data from astronomical data bases and multiwavelength surveys, the catalogue offers positions, sizes, distances, morphological classifications, star formation rates, stellar masses, metallicities, and nuclear activity classifications. This wealth of information can enable a wide range of applications, such as (i) demographic studies of extragalactic sources, (ii) initial characterization of transient events, and (iii) searches for electromagnetic counterparts of gravitational-wave events. The catalogue is publicly available to the community at a dedicated portal, which will also host future extensions in terms of the covered volume and data products.