The Ultraviolet Near Infrared Optical Northern Survey (UNIONS) is a photometric survey (u,g,r,i,z) that provides answers to fundamental questions in astrophysics, including the properties of dark matter, the growth of structure in the Universe from Galactic to cluster scales, the assembly of the Milky Way, and will culminate by directly contributing to a Stage IV dark energy measurement by providing the key ground-based photometry for the ESA Euclid space mission to derive photometric redshifts. UNIONS brings together more than 200 astronomers from the international community and is a close collaboration of three major Hawaii-based facilities - the Subaru Telescope, Pan-STARRS, and the Canada-France-Hawaii Telescope (CFHT) - to enable new science in the era of survey astronomy. A critical part of the original motivation to obtain these data was provided by opportunities relating to the Euclid mission. However, UNIONS exists as an entirely separate entity from Euclid, and has a strategic purpose and expected impact extending far beyond the Euclid mission. It is becoming the definitive deep, wide optical survey of the northern hemisphere throughout the 2020s and beyond. This talk is aimed at advertising this survey to all French scientists interested in large surveys as a worthy precursor to Euclid and LSST.
