A system near the Klingon-Romulan border to which Picard ordered his blockade fleet to withdraw in 2368 so that its tachyon detection net could be re-formed.
Gamma Eridon is named in the second part of the Next Generation story Redemption. Picard has strung a line of Starfleet ships along the border, linked by tachyon beams, to expose the cloaked Romulan convoys supplying the Duras family in the Klingon civil war.
Sela answers by flooding part of the net with tachyons, blinding the area around the USS Sutherland under Data's temporary command. Picard orders every ship to fall back to Gamma Eridon and rebuild the grid there before the Romulans slip through.
Data judges that there is no time and stays where he is, in defiance of the order. He uses photon torpedoes to light up the residual tachyon traces on the Romulan hulls, revealing the convoy and forcing it to turn back.