A measurement of event-shape variables in proton-proton collisions at largemomentum transfer is presented using data collected at $\sqrt{s} = 13$ TeV withthe ATLAS detector at the Large Hadron Collider. Six event-shape variablescalculated using hadronic jets are studied in inclusive multijet events usingdata corresponding to an integrated luminosity of 139 fb$^{-1}$. Measurementsare performed in bins of jet multiplicity and in different ranges of the scalarsum of the transverse momenta of the two leading jets, reaching scales beyond 2TeV. These measurements are compared with predictions from Monte Carlo eventgenerators containing leading-order or next-to-leading order matrix elementsmatched to parton showers simulated to leading-logarithm accuracy. At low jetmultiplicities, shape discrepancies between the measurements and the MonteCarlo predictions are observed. At high jet multiplicities, the shapes arebetter described but discrepancies in the normalisation are observed.