Deneb II was the second planet of the Deneb system. This planet was aligned directly between Earth and Argelius II.
Sometime prior to 2266, Deneb II was the site of several murders of women committed by the Redjac entity, incarnated as "Kelsa". (TOS: "Wolf in the Fold")
Deneb II (Deneb Kaitos II) was located in the Alpha Quadrant. This planet was colonized by Deneb V (Deneb Kaitos V) in the late 21st century. Deneb II was classified as Class M. This planet was a member of the Federation. (Star Trek: Star Charts, pages 33, 41, & United Federation of Planets I)