  Generalized CP symmetry of order 4 (CP4) is surprisingly powerful in shaping
scalar and quark sectors of multi-Higgs models. Here, we extend this framework
to the neutrino sector. We build two simple Majorana neutrino mass models with
unbroken CP4, which are analogous to Ma's scotogenic model. Both models use
three Higgs doublets and two or three right-handed (RH) neutrinos. The minimal
CP4 symmetric scotogenic model uses only two RH neutrinos, leads to three
non-zero light neutrino masses, and contains a built-in mechanism to further
suppress them via phase alignment. With three RH neutrinos, one generates a
type I seesaw mass matrix of rank 1, which is then corrected by the same
scotogenic mechanism, naturally leading to two neutrino mass scales with mild
hierarchy. These minimal CP4-based constructions emerge as a primer for
introducing additional symmetry structures and exploring their phenomenological
consequences.
