Deneb II was an inhabited planet. It was the second planet of the Deneb planetary system. The system was located within the Alpha Quadrant. Others planets in the system included Deneb IV, Deneb V, and Deneb XX.
Humans began moving to this planet after 2156. Between 2156 and 2266, Deneb II was the site of several murders of women committed by the Redjac entity, incarnated as "Kelsa". (TOS: "Where No Man Has Gone Before", "I, Mudd", "Wolf in the Fold"; Star Trek VI: The Undiscovered Country, production art; DS9: "Whispers")