Cygnus IV was a planet located in the galaxy's Alpha Quadrant, the fourth planet in the Cygnus star system. Located in or near Federation space, Cygnus IV is the homeworld of the Megasoid civilization. (ST comic: "Who's Who in Star Trek, Issue 1")
Cygnus IV was also the site of a Federation scientific outpost. Sometime prior to the year 2368, Doctors David Prescott and Laura Prescott were assigned to Cygnus IV. (TNG - Strange New Worlds II short story: "Calculated Risk")
On stardate 42372.5 after encountering Q, the USS Enterprise was in orbit of Cygnus IV. (TNG novel: Imzadi)
Appendices[]
The Planet is also mentioned in the script of TNG episode: "Encounter at Farpoint":
1 EXT. SPACE - STARSHIP (OPTICAL) The U.S.S. Enterprise NCC 1701-D traveling at warp speed through space. PICARD V.O. Captain's log, stardate 42353.7. Our destination is planet Cygnus IV, beyond which lies the great unexplored mass of the galaxy.
But this line didn't make it into the final Episode.