  We develop for the first time a microscopic global nucleon-nucleus optical
potential with quantified uncertainties suitable for analyzing nuclear reaction
experiments at next-generation rare-isotope beam facilities. Within the
improved local density approximation and without any adjustable parameters, we
begin by computing proton-nucleus and neutron-nucleus optical potentials from a
set of five nuclear forces from chiral effective field theory for 1800 target
nuclei in the mass range 12 $\leq$ A $\leq$ 242 for energies between 0 MeV $<$
E $\lesssim$ 150 MeV. We then parameterize a global optical potential for each
chiral force that depends smoothly on the projectile energy as well as the
target nucleus mass number and isospin asymmetry. Uncertainty bands for elastic
scattering observables are generated from a full covariance analysis of the
parameters entering in the description of our global optical potential and
benchmarked against existing experimental data for stable target nuclei. Since
our approach is purely microscopic, we anticipate a similar quality of the
model for nucleon scattering on unstable isotopes.
