To develop approaches for treating human skeletal muscle aging and related diseases, it is imperative to gain a comprehensive understanding of human skeletal muscle aging. In this study, the authors generated the single-nucleus transcriptomic atlas of NHP skeletal muscle aging, and identified a panel of nuclear types with distinct and unique gene expression signatures. The authors also identified and experimentally validated the downregulation of FOXO3 causally triggered human skeletal muscle aging. This study provides a valuable resource for understanding the mechanistic underpinning of primate skeletal muscle aging, and facilitates the development of novel therapeutical intervention strategies to combat age-associated muscle degenerative disorders.