  Multiple stellar populations (MPs) representing star-to-star light-element
abundance variations are common in nearly all ancient Galactic globular
clusters. Here we provide the strongest evidence yet that the populous, ~ 1.7
Gyr-old Large Magellanic Cloud cluster NGC 2173 also exhibits light-element
abundance variations. Thus, our results suggest that NGC 2173 is the youngest
cluster for which MPs have been confirmed to date. Our conclusion is based on
the distinct bifurcation at the tip of its red-giant branch in high-quality
color--magnitude diagrams generated from Hubble Space Telescope imaging
observations. Our results are further supported by a detailed analysis of
'pseudo-$UBI$' maps, which reveal clear evidence of a bimodality in the
cluster's red-giant-branch color distribution. Young clusters in the Magellanic
Clouds can provide critical insights into galaxy evolution histories. Our
discovery of MPs in NGC 2173 suggests that ancient Galactic globular clusters
and young massive clusters might share a common formation process.
