Here, the authors provide a comprehensive understanding of the cell-type-specific mechanisms underlying primate ovarian aging at single-cell resolution. The authors surveyed the single-cell transcriptomic landscape of ovaries from young and aged non-human primates (NHPs) and identified seven ovarian cell types with distinct gene-expression signatures, including oocyte and six types of ovarian somatic cells. Indepth dissection of gene-expression dynamics of oocytes revealed four subtypes at sequential and stepwise developmental stages. The authors found that oxidative damage is a crucial factor in ovarian function decline with age. The study revealed new diagnostic biomarkers and potential therapeutic targets for age-related human ovarian disorders.