Many of the galaxies which we see scattered across the sky are members of groups or clusters. In some cases, it is easy to find references which detail the membership of such groups; in others, not so easy. This page will collect various group listings, and provide links to Sky Atlas entries (and where appropriate, to Online Text pages) for members of such groups. Its organization will place all the groups in one reference paper in the order they are presented in that paper; but the listings for various reference papers and the groups discussed in those papers will proceed in a haphazard manner -- namely, as I create Sky Atlas entries for individual galaxies which prove to be members of a particular group, I will post the corresponding list of group members on this page. For groups not yet listed, refer to the original papers.