This work is licensed under a Creative Commons Attribution 4.0 International License.An observation of electroweak W ± Z production in association with two jets in proton–proton collisions is presented. The data collected by the ATLAS detector at the Large Hadron Collider in 2015 and 2016 at a centre-of-mass energy of √s = 13 TeV are used, corresponding to an integrated luminosity of 36.1 fb−1. Events containing three identified leptons, either electrons or muons, and two jets are selected. The electroweak production of W ± Z bosons in association with two jets is measured with an observed significance of 5.3 standard deviations. A fiducial cross-section for electroweak production including interference effects and for a single leptonic decay mode is measured to be σW Zjj−EW = 0.57 +0.14−0.13 (stat.) +0.07−0.06 (syst.) fb. Total and differential fiducial cross-sections of the sum of W ± Zjj electroweak and strong productions for several kinematic observables are also measured
