Described herein are compositions and methods relating to molecular cerium-oxide nanoclusters. In an aspect, described herein are methods of synthesizing molecular cerium-oxide nanocluster compositions and compositions thereof. In an aspect, described herein are methods of scavenging reactive oxygen species utilizing molecular cerium-oxide nanoclusters as described herein. Also described herein are pharmaceutical compositions and methods of use. Pharmaceutical compositions as described herein can comprise a therapeutically effective amount of a compound (such as a composition comprising one or more molecular cerium-oxide nanoclusters), or a pharmaceutically acceptable salt of the compound, and a pharmaceutically acceptable carrier. Methods of treating oxidative stress are also described herein, comprising administering pharmaceutical compositions as described herein to a subject in need thereof. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.