2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/9814We report the serendipitous discovery of a giant grvitational arc in the Abell Supplementary cluster S295 during optical follow-up observations of clusters detected in the ROSAT All-Sky Survey. The cluster has a redshift z=0.3007 and a velocity dispersion of about 900 km/sec. This is the first giant arc newly found in a ROSAT Survey cluster, indicating the potential advantage of searching for giant arcs in X-ray selected clusters.accepted by A&A (Letters); uuencoded-compressed-tarred PostScript file including 2 figures. ROSAT Clusters ESO KP e-preprint #1Astrophysicstext