The cross-section for the production of two jets in association with a leptonically decaying Z boson (Zjj) is measured in protonâproton collisions at a centre-of-mass energy of 13 TeV, using data recorded with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fbâ1. The electroweak Zjj cross-section is extracted in a fiducial region chosen to enhance the electroweak contribution relative to the dominant DrellâYan Zjj process, which is constrained using a data-driven approach. The measured fiducial electroweak cross-section is ÏEWZjj= 119Â±16(stat.)Â±20(syst.)Â±2(lumi.) fb for dijet invariant mass greater than 250 GeV, and 34.2Â±5.8(stat.)Â±5.5(syst.)Â±0.7(lumi.) fb for dijet invariant mass greater than 1 TeV. Standard Model predictions are in agreement with the measurements. The inclusive Zjj cross-section is also measured in six different fiducial regions with varying contributions from electroweak and DrellâYan Zjj production.