CERN-LHC. Measurement of the cross section for electroweak production and constraints on anomalous quartic couplings from events with a W boson and a photon in association with two jets in proton-proton collisions at sqrt(s) = 13 TeV. The W boson candidates are selected through their decay into a electron or muon and corresponding neutrino. The process of interest, electroweak W gamma jj production, is isolated by selecting events with a large dijet mass and a large pseudorapidity gap between the two jets. The measurement is based on data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The observed significance of the signal is 4.9 standard deviations, where a significance of 4.6 standard deviations is expected in the standard model predictions. The results are combined with previously published CMS results based on sqrt(s)=8 TeV data, which leads to an observed (expected) significance of 5.3 (4.8) standard deviations. The measured value of the fiducial cross section for the signal is reported. Bounds are given on quartic vector boson interactions in the framework of dimension-8 effective field theory operators at 95% confidence level.