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