  Measurements of the production cross section of a $Z$ boson in association
with jets in proton-proton collisions at $\sqrt{s} = 13$ TeV are presented,
using data corresponding to an integrated luminosity of 3.16 fb$^{-1}$
collected by the ATLAS experiment at the CERN Large Hadron Collider in 2015.
Inclusive and differential cross sections are measured for events containing a
$Z$ boson decaying to electrons or muons and produced in association with up to
seven jets with $p_T > 30$ GeV and $|y| <2.5$. Predictions from different Monte
Carlo generators based on leading-order and next-to-leading-order matrix
elements for up to two additional partons interfaced with parton shower and
fixed-order predictions at next-to-leading order and next-to-next-to-leading
order are compared with the measured cross sections. Good agreement within the
uncertainties is observed for most of the modelled quantities, in particular
with the generators which use next-to-leading-order matrix elements and the
more recent next-to-next-to-leading-order fixed-order predictions.
