  We present "Custodial Naturalness" as a new mechanism to explain the
separation between the electroweak (EW) scale and the scale of potential
ultraviolet completions of the Standard Model (SM). We assume classical scale
invariance as well as an extension of the SM scalar sector custodial symmetry
to $\mathrm{SO}(6)$. This requires a single new complex scalar field charged
under a new $\mathrm{U}(1)_\mathrm{X}$ gauge symmetry which partially overlaps
with $B-L$. Classical scale invariance and the high-scale scalar sector
$\mathrm{SO}(6)$ custodial symmetry are radiatively broken by quantum effects
that generate a new intermediate scale by dimensional transmutation. The little
hierarchy problem is solved because the Higgs boson arises as an elementary
(i.e. non-composite) pseudo-Nambu-Goldstone boson (pNGB) of the spontaneously
broken $\mathrm{SO}(6)$ custodial symmetry. The minimal setting has the same
number of parameters as the SM and predicts new physics in the form of a heavy
$Z'$ with fixed couplings to the SM and a mass of
$m_{Z'}\approx4-100\,\mathrm{TeV}$, as well as a light but close-to invisible
dilaton with a mass $m_{h_\Phi}\approx75\,\mathrm{GeV}$.
