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Diabetic retinopathy (DR) is the most prevalent type of retinal vasculopathy and the most widespread cause of preventable blindness in adults. Excessive increases in reactive oxygen species (ROS) and vascular endothelial growth factor are major initiators and drivers of DR progression, respectively. However, current DR treatment options remain limited, particularly for early DR. Nanotechnology‐mediated antioxidant strategies are gaining increasing popularity to treat ocular diseases. Quercetin has excellent ROS scavenging efficiency but poor stability and low bioavailability in physiological environments. In this study, ultrasmall Fe‐Quer nanozymes (NZs) formed by coupling quercetin with low‐toxic iron ions are reported that can mimic the activities of three important antioxidant enzymes, superoxide dismutase, catalase, and peroxidase, thereby exhibiting excellent water dispersion and efficient ROS scavenging ability. In vitro and in vivo assays validate the effects of Fe‐Quer NZs against inflammation, oxidative stress damage, microvascular leakage, and angiogenesis, particularly their vascular protective effect in early DR. Transcriptomic analysis further reveals a potential multitarget‐specific therapeutic mechanism of Fe‐Quer NZs against DR. These observations open avenues for Fe‐Quer NZs, composed of molecules of a natural product and metal ions with artificial NZ activity, as microvascular protective agents for DR and other ROS‐related diseases. [ABSTRACT FROM AUTHOR]