The Pleiades Cluster was a star cluster. Velara III and an unnamed starbase were located near this cluster. (TNG: "Home Soil")
An image appearing to be this cluster was contained in the Enterprise computer in 2254, when the Talosians scanned Enterprise's records. (TOS: "The Cage")
On Stardate 41463.9, the USS Enterprise-D was mapping the cluster. (TNG: "Home Soil")
While on a date, on a holographic recreation of Mars, with Denara Pel, The Doctor pointed out the Pleiades Cluster as among the many star formations and astronomical highlights seen from Mars. (VOY: "Lifesigns")
According to the Star Trek: Star Charts ("United Federation of Planets II"), the Pleaides Cluster was located in non-aligned space, in the Alpha Quadrant.
An unused image of the Talos IV
surface prepared for "The Cage
" showed the Pleiades very prominently in the Talos sky, the brightest stars enlarged to the size of suns.