  Non-supersymmetric SO(10) grand unified theories provide a framework in which
the stability of dark matter is explained while gauge coupling unification is
realized. In this work, we systematically study this possibility by classifying
weakly interacting DM candidates in terms of their quantum numbers of
$\text{SU}(2)_L \otimes \text{U}(1)_Y$, $B-L$, and $\text{SU}(2)_R$. We
consider both scalar and fermion candidates. We show that the requirement of a
sufficiently high unification scale to ensure a proton lifetime compatible with
experimental constraints plays a strong role in selecting viable candidates.
Among the scalar candidates originating from either a 16 or 144 of SO(10), only
SU(2)$_L$ singlets with zero hypercharge or doublets with $Y=1/2$ satisfy all
constraints for $\text{SU}(4)_C \otimes \text{SU}(2)_L \otimes \text{SU}(2)_R$
and $\text{SU}(3)_C \otimes \text{SU}(2)_L \otimes \text{SU}(2)_R \otimes
\text{U}(1)_{B-L}$ intermediate scale gauge groups. Among fermion triplets with
zero hypercharge, only a triplet in the 45 with intermediate group
$\text{SU}(4)_C \otimes \text{SU}(2)_L \otimes \text{SU}(2)_R$ leads to
solutions with $M_{\rm GUT} > M_{\rm int}$ and a long proton lifetime. We find
three models with weak doublets and $Y=1/2$ as dark matter candidates for the
$\text{SU}(4)_C \otimes \text{SU}(2)_L \otimes \text{SU}(2)_R$ and
$\text{SU}(4)_C \otimes \text{SU}(2)_L \otimes \text{U}(1)_R$ intermediate
scale gauge groups assuming a minimal Higgs content. We also discuss how these
models may be tested at accelerators and in dark matter detection experiments.
