  Inclusive isolated-photon production in $pp$ collisions at a centre-of-mass
energy of 13 TeV is studied with the ATLAS detector at the LHC using a data set
with an integrated luminosity of 3.2 fb$^{-1}$. The cross section is measured
as a function of the photon transverse energy above 125 GeV in different
regions of photon pseudorapidity. Next-to-leading-order perturbative QCD and
Monte Carlo event-generator predictions are compared to the cross-section
measurements and provide an adequate description of the data.
