  The study of quarkonia, bound states of heavy (charm or bottom)
quark-antiquark pairs such as the J/psi or the Upsilon?, provides insight into
the earliest and hottest stages of high-energy nucleus-nucleus collisions where
the formation of a Quark-Gluon Plasma is expected. High-precision data from
proton-proton collisions represent an essential baseline for the measurement of
nuclear modifications in nucleus-nucleus collisions and serve also as a crucial
test for models of quarkonium hadroproduction. Another fundamental tool to
understand the quarkonium production in nucleus-nucleus collisions is the the
study of proton-nucleus interactions, which allows one to investigate cold
nuclear matter effects, such as parton shadowing or gluon saturation. The ALICE
detector provides excellent capabilities to study quarkonium production at the
Large Hadron Collider at both central and forward rapidity. An overview on
ALICE results on quarkonium production in pp, p-Pb and Pb-Pb collisions is
presented. Results are compared to theoretical model predictions.
