2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/12988The paper describes the goals and first results of the ROSAT ESO Flux-Limited X-ray (REFLEX) Cluster Survey, a redshift survey of the X-ray brightest galaxy clusters in the ROSAT All-Sky Survey in the southern hemisphere conducted in the frame of an ESO key programme.12 pages, 7 figures, submitted to the ESO MessengerAstrophysicsProbing the Cosmic Large-Scale Structure with the REFLEX Cluster Survey : Profile of an ESO Key Programmetext