The Fornax Cluster is a cluster of galaxies lying at a distance of 19 megaparsecs (62 million light-years). It has an estimated mass of (7±2)×10¹³ solar masses, making it the second richest galaxy cluster within 100 million light-years, after the considerably larger Virgo Cluster. It may be associated with the nearby Eridanus Group. It lies primarily in the constellation Fornax, with its southern boundaries partially crossing into the constellation of Eridanus, and covers an area of sky about 6° across or about 28 sq degrees.

The Fornax Cluster is a particularly valuable source of information about the evolution of such clusters due to its relatively close proximity to the Sun. It also shows the gravitational effects of a merger of a galaxy subgroup with the main galaxy group, which in turn lends clues about the associated galactic superstructure. At the centre of the cluster lies NGC 1399. Other cluster members include NGC 1316 (the group's brightest galaxy), NGC 1365, NGC 1427A, NGC 1427 and NGC 1404.

Fornax can be divided into two subclusters: the main cluster, centered on NGC 1399, and a subgroup 3 degrees to the southwest centered on the lenticular galaxy NGC 1316 that is currently in the process of infalling with the largest subcluster to merge with it, and whose galaxies are experiencing relatively strong star formation activity.

As with many other galaxy clusters, Fornax intracluster medium is filled with a hot, rarefied gas that emits X-rays. and contains a number of intergalactic stars, some of which have produced novae.

(*) - Membership is uncertain