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