  A search for heavy long-lived multi-charged particles is performed using the
ATLAS detector at the LHC. Data collected in 2015-2018 at $\sqrt{s}$ = 13 TeV
from $pp$ collisions corresponding to an integrated luminosity of 139 fb$^{-1}$
are examined. Particles producing anomalously high ionization, consistent with
long-lived spin-1/2 massive particles with electric charges from $|q|=2e$ to
$|q|=7e$ are searched for. No statistically significant evidence of such
particles is observed, and 95% confidence level cross-section upper limits are
calculated and interpreted as the lower mass limits for a Drell-Yan plus
photon-fusion production mode. The least stringent limit, 1060 GeV, is obtained
for $|q|=2e$ particles, and the most stringent one, 1600 GeV, is for $|q|=6e$
particles.
