Polycystic ovarian syndrome (PCOS) is considered the most prevalent endocrinological disorder, which affects some women and it is characterized by anovulation and hyperandrogenism, with morphologic changes in the ovary, inappropriate gonadotropin secretion, and insulin resistance (IR) with accompanying compensatory hyperinsulinemia. PCOS was associated with some degree of IR which probably contributes to hyperandrogenism. Many studies showed that metformin, when used to treat PCOS, significantly reduced serum androgen levels, improved insulin sensitivity, restored menstrual cyclicity, and was successful in triggering ovulation. As a result, metformin may be useful in treating PCOS-related infertility. The aim of this review was to clarify PCOS, its prevalence, particularly in Saudi Arabia, its pathogenesis, its impact on the patient's health, and to explain the uses of metformin, its mechanism of action, and its role in the treatment of PCOS-related infertility.