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")