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Age-associated decreases in follicle number and oocyte quality result in a decline in female fertility, which is associated with increased infertility. Granulosa cells play a major role in oocyte development and maturation both in vivo and in vitro. However, it is unclear whether a reduction in cryptochrome 1 (Cry1) expression contributes to granulosa cell senescence, and further exploration is needed to understand the underlying mechanisms. In this study, we investigated the role of Cry1, a core component of the molecular circadian clock, in the regulation of senescence in ovarian granulosa cells. Western blotting and qRT-PCR showed that Cry1 expression was downregulated in aged human ovarian granulosa cells and was correlated with age and anti-Müllerian hormone (AMH) levels. RNA-seq analysis suggested that ferritinophagy was increased after Cry1 knockdown in KGN cells. MDA, iron, and reactive oxygen species (ROS) assays were used to detect cellular ferritinophagy levels. Ferroptosis inhibitors, iron chelators, autophagy inhibitors, and nuclear receptor coactivator 4 (NCOA4) knockdown alleviated KGN cell senescence induced by Cry1 knockdown. Immunofluorescence, immunoprecipitation, and ubiquitination assays indicated that Cry1 affected NCOA4 ubiquitination and degradation through HERC2, thereby affecting NCOA4-mediated ferritinophagy and causing granulosa cell senescence. KL201, a Cry1 stabilizer, enhanced ovarian function in naturally aged mice by reducing ferritinophagy. Our study reveals the potential mechanisms of action of Cry1 during ovarian aging and provides new insights for the clinical treatment of age-related fertility decline. A proposed molecular model of Cry1 in regulating senescence of human granulosa cells. Cry1 depletion reduced the expression of the E3 ubiquitin ligase HERC2, which reduced the ubiquitination and degradation of NCOA4, thereby promoting ferritinophagy and inducing granulosa cell senescence. [Display omitted] • Cry1 expression is downregulated in aged human ovarian granulosa cells. • Cry1 induces KGN cell senescence through NCOA4-mediated ferritinophagy. • Cry1 affects NCOA4 ubiquitination and degradation through HERC2. • Cry1 stabilizer KL201 enhances ovarian function by reducing ferritinophagy in middle-aged mice. [ABSTRACT FROM AUTHOR]