  We argue that extensions of the Standard Model (SM) with a warped extra
dimension, which successfully address the hierarchy and flavor problems of
elementary particle physics, can provide an elegant explanation of the 750 GeV
diphoton excess recently reported by ATLAS and CMS. A gauge-singlet bulk scalar
with ${\cal O}(1)$ couplings to fermions is identified as the new resonance
$S$, and the vector-like Kaluza-Klein excitations of the SM quarks and leptons
mediate its loop-induced couplings to photons and gluons. The electroweak gauge
symmetry almost unambiguously dictates the bulk matter content and hence the
hierarchies of the $S\to \gamma\gamma$, $WW$, $ZZ$, $Z\gamma$, $t\bar t$ and
dijet decay rates. We find that the $S\to Z\gamma$ decay mode is strongly
suppressed, such that $\mbox{Br}(S\to
Z\gamma)/\mbox{Br}(S\to\gamma\gamma)<0.1$. The hierarchy problem for the new
scalar boson is solved in analogy with the Higgs boson by localizing it near
the infrared brane. The infinite sums over the Kaluza-Klein towers of fermion
states are finite and can be calculated in closed form with a remarkably simple
result. Reproducing the observed $pp\to S\to\gamma\gamma$ signal requires
Kaluza-Klein masses in the multi-TeV range, consistent with bounds from flavor
physics and electroweak precision observables.
  Useful side products of our analysis, which can be adapted to almost any
model for the diphoton resonance, are the calculation of the gluon-fusion
production cross section $\sigma(pp\to S)$ at NNLO in QCD, an exact expression
for the inclusive $S\to gg$ decay rate at N$^3$LO, a study of the $S\to t\bar t
h$ three-body decay and a phenomenological analysis of portal couplings
connecting $S$ with the Higgs field.
