Introduction: Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder affecting women of reproductive age and is characterized by metabolic and reproductive dysfunction. Vitamin D deficiency is highly prevalent in women with PCOS and has been associated with insulin resistance, hyperandrogenism, menstrual irregularities, and chronic low-grade inflammation. Understanding this association may help refine management strategies for PCOS. Methods: A structured literature review was conducted using PubMed, Google Scholar, ScienceDirect, and ResearchGate to identify peer-reviewed human studies published between January 2015 and July 2024. Studies examining clinical, molecular, genetic, and therapeutic aspects of vitamin D in PCOS were included, while animal studies and articles unrelated to PCOS were excluded. Results: Evidence from observational studies and meta-analyses indicates that vitamin D deficiency is common in women with PCOS and correlates with increased insulin resistance, elevated androgen levels, and inflammatory markers. A pooled analysis of 20 randomized controlled trials (n=1961) demonstrated that vitamin D supplementation was associated with improvements in ovulation and pregnancy rates, reductions in early miscarriage risk, and favorable changes in androgen levels and metabolic parameters. Proposed mechanisms include modulation of insulin signaling, steroidogenesis, inflammatory pathways, and vitamin D receptor–mediated gene expression. However, heterogeneity in dosing regimens and treatment duration limits definitive clinical recommendations. Conclusion: Vitamin D deficiency appears to contribute to metabolic and reproductive dysfunction in PCOS. Supplementation shows potential benefits, particularly in women with documented deficiency, but standardized dosing strategies and long-term outcome data are needed. Addressing vitamin D status may represent an adjunctive component of comprehensive PCOS management.